I will be doing a V4 version. For V4, I've been working with the simplest addons first to both learn V4 and find out what doesn't work any more an how to invest the many many hours it takes to covert an addon from V3 to V4 with no increase in functionality… Currently working on beta testing auto_mail but will probably look at doing mailchimp next. Trouble is it takes a lot of time to catch all the annoying changes in V4 that only show up in run-time testing.
Awesome!