There are some interesting challenges in here for the long term.

Federation between different implementations of forges sounds great.

If a well-known forge like Gitlab adopts this then others might follow suit, including perhaps even Github. However, given how much ActivityPub leaves up to the implementation I wonder if seamless interop between forges from different vendors will ever be more than a dream even if everyone adds ActivityPub?
It's going to be hard enough just getting this working among all the Git-based forges. There are and will be forges based on other version control systems which may or may not interoperate all that well with Git.

Moderation is another concern. I don't mind randos or honkers jumping into casual conversations I have on Mastodon. But issue trackers and code review tools require a huge amount of (self-)moderation to work effectively. The idea of plumbing Mastodon into my development tools in this way scares me a bit. It's cool if Mastodon can follow public discussion of bugs as they happen in the issue tracker but would developers really want casual social media conversations merged in there?