I just found an FIA quote:
"The date for introduction of the 1600cc turbo engine for the WRC car
has been brought forward to 2011 to bring it in line with the engine
used in the cars on sale to the public."
Very convenient for the 2011 mini 4wd entry. I look forward to this regulation change, it should see some new entries to the sport and more WRC versions of road cars, the mini being one obviously. This could open the way to Peugeot 207, Ford Fiesta, Vauxhall Corsa (if they have the money) WRC cars.
These cars are all large in size now and suited to being the full WRC spec competitive 4wd class cars.
I'm guessing they will still be 300bhp cars. So i expect some monster 1.6 engines.