Holding off for the 50th probably would not be wise, IMHO, as Paramount likes to put a hold on licensed items being approved so they can control the marketing for a new movie released.
I believe part of the rush the labels are having to get the Star Trek scores out in general may be due to the new movie in 2013, and Paramount don't want to crowd the market with TOS merchandising.
When the ST:TMP 20th Anniversary Set was announced, the release was delayed until Insurrection had been put out there, much to the annoyance of both Star Trek fans and Soundtrack collectors at the time.
When a label gets the chance to do something like this, they cannot wait for other parties to change their minds. When the stars align, they have to go for it right there and then.