They've got 20 days to beta, and 2.3 months to launch. 4 week cert on all platforms.Fair enough.
But consider that even though Bungie dropped PS3/X360 support, they are, in a way, supporting more platforms than before -- while still supporting D1 up until earlier this year. Also, X1X doesn't even release until November, so perhaps they're not even at a stage yet where they can confirm 4K (even though I think it's pretty much guaranteed). Not to mention the game is still in development. Who knows, maybe they're still optimizing to get Pro up to 4K.
Beta is sent in for cert probably last week, network test for the beta, then 1.3 months to launch.
Being realistic, if they are struggling to reach 4K on 4Pro today, the situation doesn't bode well for 1X enhanced version at launch.