That's what's happened.
The Thieves Guild patch also ended the ability to play if you had a pre-DX10 set up.
Now it doesn't affect me (and I'm successfully running the newer 64bit option), but there's a growing list of people who have been playing this game for years and now find themselves suddenly frozen out.
Needless to say there is a mounting level of dissatisfaction, (that's the calmer description), as people find out this is the cause of their game instantly crashing when trying to play after yesterday's Thieves patch.
Now not everyone has money available to suddenly upgrade their pc, so it appears Zenimax have successfully dropped a portion of their player-base overnight.
Irrespective of personal opinions on whether everyone should or should not have a DX10 capable rig, to alienate some long standing players, literally overnight, is an extremely poor decision making process.