Not in applications that can't use 4 cores which is the majority.
But that's already true today with dual-core vs. quad-core, so how does tri-core make any difference? It's going to be outperformed on properly multi-threaded apps by quad-core (even if the quad-core is lower frequency), and outperformed on non-threaded apps by higher clocked dual-core.
I see this (again, if it happens) as a bizarre segmentation play that isn't going to help AMD at all in the long term, and is a waste of engineering resources.
-=spaark=-