I could be wrong, but I think the online service won't go up until the PS3 launches. There was a large talk of it coming out before april, but it is obviously nowhere in sight. I don't think it would be smart for them to open up their online community before the PS3 launches, though. To release it now would mean that players would get used to it on the PS2 and then immediately have to relearn everything with the PS3. I say look for it in november, or maybe late october.
As for a secondary drive for the PS3, that I haven't heard. Ive only heard the thing about the HDD being either seperate or built in, which is now confirmed as being built in. I don't know of any way that the memory or power for the PS3 will be upgradable. I have heard, however, that Nintendo might put out memory upgrades for the Revolution so that people can download more of the classic games. The Revolution is supposedly going to ship with 512G worth of memory space, and there are talks of putting out an additional add-on or a type of Revolution exclusive flash memory card. But, nintendo is being nintendo, and nobody knows much past a few veiled comments their higher ups have made. besides, the download games only take up, at most, 1G of hard-drive space (and thats just for the N64 games).