I wonder what caused them to change tact - To ensure continuity between HTV & CBS over a season cliffhanger? If I'm correct, expect to see Times Arrow and Descent in your theatre's rather than Unification and Chain of Command.
I think they are choosing based on appeal to general audiences. People would not buy a full seasons. So subjects which are popular, The Borg and the Klingons. You can tell by the cover art. Its similar to the themed Fan Collective sets.
So I have no doubt this will be done with Unification. Its an easy sell. I have heard TOS fans complain that they want the guest appearances episodes without needing to buy the whole seasons. I could see causal fans, whether older or from the new films, being curious to see it too.
Also I think being a two parter within a season, it works better as a movie than some of the later cliffhangers. Which were not written to be seen as a movie. The cliffhangers often felt like having a climax in the middle of a movie, so that the second have was usually a let down. The first part of Unification is a build up, the Search for... Spock.
So I think it actually plays much better as a movie than as two separate episodes.