Although Ubisoft hasn't officially confirmed it, the UK gaming magazine NGamer has a one page "centerfold" with preliminary screenshots and the announcement of RRR2.

As one of the first Wii games I bought and played, I'm looking forward to this one. Actually, my 8 year old sone is also looking forwrad to it more than I am. He was so excited when he completed the game that he then realized there were no more new levels and he almost started to cry. I assured him that they would make a Raving Rabbids 2 and that calmed him down.  Thanks Ubisoft for making my son so happy!