It's important to note that Ballmer did not say the devices would actually be on sale in time for Christmas, but the implication might be there. More importantly, he did not say who would make them. The 8.9-inch HP Slate is most likely a candidate, especially considering it was was first announced at CES in January by Ballmer himself. Still, given that it's supposed to be for enterprise-use only, meaning consumers like you and me won't be able to buy it, we're hoping there will be many others (and rumors about Microsoft working with OEMs on at least one tablet device are keeping us hopeful).
Tablet progress aside, the emphasis next week will no doubt still be on Windows Phone 7. "The job right now is we've got to get back seriously into the game of phones," Ballmer told Reuters. "We've got to have a comeback against the competition and I think with our new Windows phones we really have a beautiful product."