I know this wouldn't exactly be possible in current verse, but what if you got chance to play these groups in the past, and could change certain outcomes, like Snow Elves being banished, the Dwemer search for knowledge destroying them or much more. It's just idea had while chatting to Nova on skype.

DLC with more playable races would be nice. Like the Snow Elves (Falmer) or Akavari. However, I don't really know about DLC that takes place with a totally different character than the one we play as now.

Not sure about it being possible either, but it would be awesome to see/experience some of the events we read and hear about in Skyrim first hand.

It certainly sounds like some of those past events relating to extinct races like the Snow-elves are better thought out than say, the war between the Stormcloaks and Imperials was. In Skyrim we already get to experience something similar with past events don't we? I don't want to include spoilers here so I will not elaborate, but most will know what I mean. That way, we wouldn't really have to worry about creating a sort of paradox either - it just has to be done properly. (Maybe Dwemer technology could play a role in it?)

If it's included in a quest line related to current events it would be really neat.

I don't think we'll see any more races in TES unless they decide to make a game based in Akavir, but I've heard that Bethesda has said that they'll never do that.. so.. don't hold your breath.

We definitely will NOT see any races from Akavir in Tamriel. Akavir has tried to invade Tamriel and Tamriel has tried to invade Akavir, but they both failed miserably, so there's no way that anyone from Akavir is going to come to Tamriel and survive.

if you make a DLC that has playable, extinct races... doesn't that mean that they are no longer extinct?

Nah. It would be horrible.

While this has some possible fun potential for an "offshoot" game ( that would be, one that's set in this universe but is NOT part of the "established game structure") it wouldn't fit at all at this point in time.