June 3 seems the most likely to me. May is too crowded, and Nov 23 is the (supposed) release of Giants. Opening against Sausage Party wouldn't hurt ST3 too bad, plus it has 2 weeks until Finding Dory/HTTYD3, and in between, it'll have to face against Uncharted, which may still be big, but I don't think it'll scare Paramount away from the date. July as it stands is much much too crowded already, even though a lot of stuff will most likely move.
There's also the fact that BvS, Alice and Dragon 3 will all probably move, and any of these dates is possible.
Then again, Paramount may opt for the Nov 11 date, and force Sony to move Sinister Six...