Gotta be Diablo 3! That purple 'monster' seems a lil cartoonish tho... but hmm, every thing named ice and thundra also throws in some screws in the gears of imagination

Hell Froze Over theme IMO.
Hopefully D3.

I'm hoping for D3 as well but blue has never been in the diablo palette. I wish the splash looked more like this

It won't be WOTKL, I guess the rune is just a coincidence or something to play with our minds. WOTKL was announced, posting a teaser for it is stupid.

I think in that splash screen is the cave where Arthas took the Frostmourne In image where only a part of the monster is shown, it very might be a new race in WotLK, let's say, Arctic Tauren And purple Diablo 3 monster is a joke

For me the most interesting thing is the splash image. More importantly, the small rune in the middle left of the image. It looks very similar to the runes used in the Diablo games. Now, granted it is also very similar to the runes used in Warcraft and on of the runes also looks like a rune used on Frostmourne. But take into consideration that Diablo was there first and has been using these similar type runes throughout it's history. Look at the runes in both the Diablo 1 and 2 manuals and also the runes in game, such as the wards on the ground in the Kurast Docks. They look very similar indeed. Of course it being Blizzard they use the same art style and artists for all their project but the runes in the splash image just have more of a Diablo feel about them. Warcraft tends to have large glowing runes,that stand on their own. While Diablo tends to have more subtle and thin ones which are part of the background. We also can;t rule out that the ice is actually the Worldstone that was destroyed by Tyrael at the end of LoD. And sure the Worldstone was red, but maybe only on this side of what it was protecting...