Well, the current major versions have been 1.0 and 1.1 (the modding update). The DLC will presumably be 1.2. It's not too difficult to downpatch to 1.0, and presumably it won't be difficult to downpatch to 1.1 either. There will be a DLC1 category for All Time Pieces, All Acts, and All Rifts, and if 1.2 changes any% (it isn't expected to) there will also be a DLC1 category for any%.

In particular, finale skip and bag skip are no longer possible on 1.1; however, faster telescope animations make 1.1 slightly faster although both versions are perfectly viable, and since bag skip is definitely not easy, 1.1 is recommended for beginners.

Also, I've heard there used to be another flying glitch in 1.0, but 1.1 has bucket flying still which is way funnier anyway.