They do. There are two Argonians in Solstheim- the boat keeper and one more who is dead. Not from anything to do with cold, but more from being thrown off an airship without slowfall or such.
Indeed, and while the boat keeper does complain about the cold, it doesn't seem to interfere with his ability to offer boat services at all. Also, players who are playing Argonians can go there just fine. In Oblivion as well, I seem to recall at least one Argonian in the Bruma Fighters Guild. In any case, if Argonians aren't playable, then I'll probably not play the game (Unless someone makes a mod adding them.) and rant about that decision to no end on these forums.
In any case, while at least I haven't seen it explicitly stated what ten races are playable, the Game Informer article seems to say there are ten races, and since the series already has ten races, and there's no mention of any new races, we can assume it's the same ten.