Okie is right about sales are all that matter in the end. After all, that's their concern with the EPA banning them in the first place.
However, it's a bit too early to talk about the CRF450 spanking the CR250 in sales. This is even more important when it comes to the CRF250 vs. CR125, KXF250 vs. KX125, etc, since they are just coming out. The bottom line is everyone wants the new thing at first -- it's just human nature. If it's been hyped by the press and advertising then all the moreso. In the case of dirt bikes, the hope it make them faster will draw them to it. This was what I pointed out way earlier in this thread.
We'll see if it really pans out that way. When average racing families who are accustomed to $100 top end kits start paying $1000-$2000 for heads, valves, and other 4 stroke engine work, they may rethink things (after paying more for the 4 stroke bikes in the first place). As an engineer, it really concerns me to see the steps the factories are going to ligthening them to make them closer to the weight of 2 strokes -- it WILL affect reliability. There is no disputing the calculus of the area under the 4 stroke torque curve being bigger than that of the 2 stroke curves, but at the mass purchasing level of bikes the economics will become important as the newness wears off.