[_ck_]

You’re asking about gravtars but then talking about uploading avatars which are two different features.

There are plugins for bbPress to show a user’s gravatar but if it’s a locally uploaded avatar within WordPress, someone would have to come up with some code to display it on the bbPress side. So it’s possible but would take someone to look at it.

The avatar upload plugin on the bbpress side has some documentation or user comments on how to access the avatar from wordpress.