First, probably not anywhere near technical feasibility for at least several years. Remember the lag when a bunch of avatars were in one place? Or how long it took for a scene to fill in after you teleported? And the bandwidth, good lord...
But then I imagine what it would be like if the bandwidth and server performance issues were magically solved. And I realize that it was all imagined before decades ago, in Snow Crash[1].
[1]http://www.amazon.com/Snow-Crash-Neal-Stephenson/dp/05535626...