Ok additionally in case anyone cares Vanguard is a no loading zone game (like Gothic 3), as mentioned before I am not expert but I don't recall of hearing of a no load MMOG before, maybe just me though.
Secondly they Unreal series of engines has not to my experience ever breached this technology before and certainly the first mainstream engine I have heard, plus the graphic level of quality and Unreal's ability to have great looking textures with excellent network capability is pretty cool at least from a technological standpoint.
DAOC only had a few loading zones, big cities mostly. You could basically run from one end of a continent to the other without having to head for a zone line.
VG still feels like it has loading zones though. Every time you cross a chunk line (basically zone line) the game freezes up and whackyness can occur. It isn't seemless but much better than running towards a gate between two outside zones.
I would think VG can get 250k people. EQ2 had that for most of the last couple of years and they survived well on it and much content was released for it. VG is fun and there is a lot to keep people entertained for a long time to come. I am just not one of those people.