V3.1 was released to address the issue of larger than acceptable heat creep issues. IMO, it is not as successful as the solution discussed in https://forum.lulzbot.com/t/dual-v3-a-review-wait-for-v4-heat-creep-still-a-problem/6017/5.
There are no firmware changes, CuraLE changes, or hotend changes. There are no changes regarding swiping, purging, or leveling.
IMO, the LulzBot TAZ 6 is end-of-life. Its replacement is the LulzBot TAZ Workhorse. The “future” of dual extrusion is the LulzBot TAZ Pro. Some new products being created by FAME (Fargo Additive Manufacturing Equipment 3D) are backwards compatible with the TAZ 6. Again IMO, a replacement for the Dual Extruder V3.1 has a very low probability of being created.
I am just an owner of a LulzBot TAZ 6 with more tool heads than I care to list. I do have a Dual Extruder V2 and a Dual Extruder V3 which I have upgraded with a fan mount as documented in the above topic.
I am happy with my Dual Extruder V3 and have done lots of dual color prints. I haven’t had as much success with PLA / PVA prints but I believe I need to do more fine-tuning of the PVA parameters.