Sorry, the relevence of the new q (which was confirmed 2 weeks ago, its no longer stylish, but looks like a vcr:() was the tv recording functions that are set to appear on the xbox 2 in the future, its online functions will be the same as the standard cube.
The reason for the cubes ability to play pso online at 56k is simple, it was designed to run on a 36k modem for the dreamcast, so 56k is just enough extra speed to lose the lag that was associated with that title, xonline however is different, again as you said with an eye to the future, and to reduce costs to microsoft themselves there are plans to copy windows xp and steal some of your bandwidth this is to be used for some kind of distributed computing model where the xboxes that are online act as part of the main server, thus vastly increasing bandwidth requirements above what would normaly be required, hence the need for broadband connections only, the idea isn't new, sony are also planning a similar system with the ps3.
i'm sure xonline will be a success in the long term with xbox 2, but in order for it to happen microsoft will need to overcome consumer resistence to having to pay twice for a game and then pay again for a larger broadband connection so as not to interfere with any homes current internet usage.
This rush to play games online may just be a few years too early for people brought up on paying for a game then taking it home and playing it, now they will be buying part of a game (still at full price) taking it home, paying for an internet connection, paying for the xonline service to download patches and level upgrades then having to pay even more to play the game online, all this will need a credit card and a friendly (and rich) parent to pay all these extra costs, and that assumes that all countries are like america where most people have a credit card, europe and africa arent like that so how are people over here going to pay for all these services, in the united kingdom, a home user cant even get a dsl connection without having a credit card.
with that said, does that mean that xbox and xbox 2 will be consoles for adults only? Basicly pricing children out of the equation altogether.