With regards to the editing, there is still time for people to go through their lists and any active or historical projects, or any popular threads they have, can be restarted on the new forum. And then throw a link to the new post on the old forum's old post with a disclaimer Due to forum software changes, any discussion about this post should be in http://www.autohotkey.com/boards/.....
Yes, people will be late to show up and will have wanted their posts edited. But for a good three month window (I guess two "officially"), people have the chance to do this. You can't please everyone who may or may not ever show up.
I've gone through similar changes where site/feature X was shutting down and migrating to site/feature Y. (This was with a game publisher transferring the license.) People were only allowed to keep their game account if in the three month announcement window they had elected to do so. (Legal reasons prevented just importing every account by default because of a ToS regarding giving information to third parties, which this new publisher would be.) You can't just postpone something indefinitely or wait so long that 99.9% of users get the news. Doing the sticky and in-site pop ups announcing the forum migration is the best thing to do. Or if emails were also sent out - I haven't gotten one, but I also don't know what email I used to register here nor do I think I've opted in for emails from AHK's forum admins - that's a good method of reaching someone, but if they're like me and have chosen not to get emails, then only the end user can be blamed.