If you guys want to have a look at the JGTC website
http://www.jgtc.net you will see that the GT-R teams will be debuting a twin-turbo V6 later this season. Most likely the basis for the new GT-R engine.
And the number of cylinders only has a little to do with how an engine revs. It has to do with displacement as well. A large v8 revs slow because of the weight of the pistons it has to pull around. where as a CART engine which is smaller revs very quickly.
But admittedly it is up to overall design.