Does that sounds correct?
Yes. And what do you think the max number of people you could have online at once in the same area of a 3D world, using BMax UDP?
Depends on a lot of things, mainly your bandwidth and how tight your loops are. Probably not more than about 50-80 tho' on the best of days on a really powerful server and with some tight UDP code. Threads are great but if one zone dies, the whole realm would die which is definitely inacceptable.
How do you figure that? If one thread should crash, it only affects the player dealing with that thread. Unless it's the main thread ofcourse, in which case all child threads (players) are disconnected. nothing to share actually.
Except "other players" for starters.