No when the servers launch and all 10-15k+ people pound it at once, it's impossible.
Vanilla is slow and tedious enough as it is; it doesn't need the extra layer of irritating. Grouping to kill named bosses is one thing; having 6 different groups camping a 5-10 minute named spawn is another. This isn't taking into account gathering, increased pool of money making the economy unmanageable, among other things. A PvP server with 15k+ people on it at once would be absolutely unplayable.
Again, there's a reason server population caps exist in every game, and it's not technical limitations.