In an ideal world? They would use such a momentous date to launch a new series on September 8, 2016. Because that would just be damn sweet!
They would also do limited theatrical re-releases of all of the previous feature films (similar scale to how they've done the TNG blu-ray revamp releases in theaters).
They would of course have Star Trek 13 come out that May.
A truly well produced documentary-level 2-hour special with interviews not only of all the actors but with historical types and such.
Some sort of big party/awards show type thing like they did for the 30th.
Now what do I really expect?
I'd like to at least have a limited theatrical release of the TOS trilogy of original films (TWOK, TSFS, TVH) where they do each film one a month, like they've done special events for the TNG blu-ray.
Some sort of TV special, aired on a major network -- CBS does own most of Trek now, so it should likely be them.