Well, let us look at next year's summer slate in depth:
Guardians of the Galaxy 2: Should be a hit, but I would be a bit surprised if it made substantially more than the first one. The Marvel movies are still performing well, but it does appear that they have a ceiling of about $400 million. The first Guardians strikes me as a "right place, right time" movie that probably already reached closed to the maximum audience it was ever going to get. That being said, it should be a shoe-in for $300 million + in the states and may increase WW from the first.
Baywatch: If the budget on this is reasonable, it could be a mid-size hit. I don't think there is much love for the Baywatch IP out there, but The Rock is well liked and his movies tend to perform well. It could be the right combo of star + concept that hits are built of these days.
Pirates 5: Flop, at least relative to budget. I think this does, at best, $150 domestic. Meanwhile, a quick googling shows reports that the budget for this thing is $320 million. That means it needs to clear a billion to even come close to being profitable.
Bad Boys 3: Like others have said, I have my doubts that this will make a June release date. Even if it does, I am not really sure what the market is for it. Bad Boys 2 was a solid hit, but it wasn't a monster or anything. If the budget is kept in check, it might be a mild success, but this definitely feels like a movie that was green-lit simply because it had a recognizable brand rather than having a brand people cared about seeing more of today.
Wonder Woman: Even though they have had terrible legs, there does seem to be initial audience interest in these DC movies. Plus, WB's marketing team continues to do a pretty good job selling these things, even if they aren't knocking them out of the park in terms of quality. I think this opens big (though maybe not as big as BvS or Suicide Squad seems poised to) and fades quickly.
The Mummy: It seems like the last few years have proved that people only really want to see Tom Cruise in Mission Impossible movies, so I am not sure how well this does. People seemed to like those Brendan Fraser Mummy movies fine, but was anyone really clamoring for a reboot of this? Or a whole connected universe of monster movies? Marketing could change my mind, but this seems like it has an uphill battle.
World War Z 2: This feels like a flop in the making. The first one wasn't a particularly large hit ($540 WW on a $200 million budget would normally be considered pretty mediocre, but it did beat the perception before release that it was going to be a huge flop). Nor do I think the first one was particularly beloved. I think general audiences liked it fine, but probably have little interest in a second helping, while the fanboys hated it. This feels like a situation where Paramount should have breathed a sigh of relief that the first one ended up performing modestly well and moved on from the idea of a sequel.
Kingsman 2: Normally, I would peg this as a hit. The first one was well liked and leggy, and a sequel seems poised to break out. I think the release date is a problem, though, as there is just so much competition all around it. I think this could perform much better in a fall/spring slot, or at least not perform any worse. Still, if the budget is as reasonable as the first, this should be a relative success.
Cars 3: Cars 2 didn't perform particularly well and wasn't particularly well liked, but the grosses of the movies are entirely besides the point for the Cars franchise. The merchandising is what matters.
Transformers 5: Huge hit overseas (especially in China), probably continues the downward trend for the series domestically. Much like Pirates 5, the budget on this thing will probably require grosses near $1 billion to even break even, a bet that seems incredibly risky for a franchise that saw a major decrease in domestic grosses between the 2nd and 3rd and 3rd and 4th installments.
Despicable Me 3: Unqualified hit, for better or worse. I think it will probably come down a bit from Despicable Me 2/Minion, but Cars 3 also strikes me as much weaker competition than Monsters University or Inside Out, and there are few other animated offering currently scheduled.
Uncharted: Apparently, there is an Uncharted movie scheduled for next June. It currently has no director or cast, though apparently Joe Carnahan just finished a draft of the script. There is no way this even comes out next summer.
Spider-Man: Seems like a safe bet to be a hit. Amazing Spider-man 2 managed to make $700 million WW despite being a terrible movie and being a follow-up to a not particularly well liked original. Plus, it had an enormous budget. Even if that last bit holds true for this film, I think Spider-Man films have a pretty high floor to begin with, and this film has the Marvel machine behind it and Iron Man in it to attract any doubters.
War for the Planet of the Apes: This one seems dependent upon marketing. People really liked the last film, but that film had pretty weak competition. This is wedged in-between Spider-Man and Dunkirk, which seems like it could be a problem. Still, if the film is as good as the last, and the marketing is solid, it seems like it could be a hit.
Dunkirk: Nolan is probably one of the only "name" directors out there, and this seems well positioned as a more "adult" offering in a summer full of sci-fi/action spectacle. If Warner didn't already have tentpoles scheduled for October (Blade Runner) and November (Justice League) and this turns out well, I would think they would move it for Oscar consideration. Still, this seems pretty well positioned to me if the marketing team does a good job.
Jumanji: Pairing The Rock and Kevin Hart together seems like a solid strategy to make this profitable. Still, Sony needs to be careful with this one. Hopefully they learned this summer that you can't spend absurd amounts on a comedy with a recognizable name and expect huge results. If they keep the budget in check, I don't see any reason this can't be as profitable as Central Intelligence was this summer. Sony just has to make sure they don't assume that just because people are aware of a brand that people want more films from that brand.
Alien: Covenant: I am not sure why Fox is releasing this strong release date (there really isn't anything else that seems likely to be a hit currently scheduled for the rest of the month) on a film that seems likely to under-perform. This is a situation that seems very similar to World War Z, in that the first film performed moderately well, but no one really loved it and there has been a long break in-between installments to further cool interest. If I were Fox, I would move Planet of the Apes or Kingsman into this slot and let them finish out the summer.
I would say that, overall, this slate seems a little better than this year's. Still, it has a whole bunch of sequels/adaptations/remakes that no one seemed to ask for that will probably have budgets that are much too large.