PSOBB Ultima will continue IMO....
Because PSO and PSO2 are both different games, and besides there is no word for an English PSO2 yet
so unless you know Japanese you wont get to play it right off the bat...
(then again an english patch might fix this up)
and another thing to consider is that PSO2 requires a LOT more PC specs than PSO, not many people (myself included)
have a PC capable of running PSO2
There's just lots of reasons why people would still play PSO anyways...