Thank you so much 
Yes, i probably underestimated that, but even if i did, to me the problem is not much the possibility for Meta to change ActivityPub, than the political one that would remain almost the same: when Meta will be fully or mostly AP compatible and will let all its Threads users follow and be followed from the rest of the Fediverse, opening the way for other big-medium sized bad shit players like maybe Microsoft, Apple, and surely down to many others, a very large part of current users of the Fediverse as it is now, certainly more than 50 percent, will be on instances which don’t block threads (and wouldn’t block the others), so, mostly out of ignorance or carelessness, they could decide, and in most cases will, to let their accounts be followed by accounts on Threads, so Meta will scrape not only their public posts, which it declaredly does, but also their “less public” posts (“followers only” posts, or the like on other Fedi platforms) too, and even “direct messages”, those which will mention at least one Threads account; all of which is total shit.
I have no illusions that a new protocol permitting its use only in open source products would be used by many from the start, and maybe it would take long for it to gain traction, or maybe it would never exit the “niche” status, but it would be good all the same even in these cases, and i think there is the possibility that it would gain a lot of traction, soon or later. But, again, i think it would be good if it existed even if it was never to exit the “niche” status.
Please have a read at this thread on the Fediverse, if and when you’re interested 
Anyway, thank you so much again for your replies