802.11g is just b but faster. They both operate under 2.4 ghz wireless frequency. B is 11 MBps, G is 54MBps (I think that's megabits per second but I could be wrong).
I use a b network right now for my computer and it works just fine.
As far as DS compatability goes, you might want to do some research on the wireless demos that you can download right now. The webpage that houses that information will list a lot of routers and wireless cards that carry specific chipsets that are compatible. I think they use an RT2560 chipset, which should be manufactured by a company called Ralink if I know my cards well enough.
Here's the page with homebrewed drivers and instructions on how to download stuff to the DS:
http://users.belgacom.net/bn967347/download.htmAnd here's a list (from the above site) that is supposed to list compatible PCMCIA cards and routers:
http://ralink.rapla.net/So I assume if you have that tech (which I don't so I can't test it myself), you should be able to communicate with the DS wirelessly (I would have killed to be able to get the Meteos demo from E3 1.5 months ago).
As far as the Revolution goes, my guess is that it will use either b or g. I'm leaning more towards G for gaming purposes (beacuse of the increased speed over b) since more data will need to be relayed as oppsoed to the DS. My guess is that DS data is far less than super 3D detailed graphics.
The next step with router tech will be PreN, but I really don't know much about that. I think they are compatible with b/g, but I'll have to research more (I'm at work, I'll reply later).
Another thing to think about: if you have 2.4ghz frequency cordless phones, you might want to look into investing in a 5.8 ghz frequency phone. Because they operate on the same signals, they *can* cause interference. It won't happen all the time, but it is best not to chance it and to keep the lines are clear as possible.