Well of course a 8 Core CPU is going to be faster than a 4 Core CPU.
My outlook on bulldozer is that it will beat Lynnfield and Bloomfield, and it'll take an 8 Core Bulldozer CPU to match a 4 Core Sandy Bridge. However, the 6-8 Core Sandy Bridge chips will beat Bulldozer handily and Ivy Bridge will widen the spread. At least that's my theory, we'll have to wait for the benchmarks before we'll know for sure.