There's 2 concerns to end times - rules and fluff. I hope against all hope that GW have seen what backlash you will get when you go for a hard-reset of the fluff - and note that a lot seemed to relate to IP - gave a chance for AoS to rename factions. In 40K we have already had that (AM, Codex Astartes etc) so I hope they see no real need.
The rules - I echo Defenestratus - we don't need 2nd-3rd levels of change - just a bit of amoebic dysentry to excrete some of the rules bloat, and a change in power levels.