Actually 2 vendors told me that, I wasn't sure if they were right!
Pentium dual cores that are in market now (as entry level budget processors E2160 E2180 etc) are actually scaled down Conroe's or I would they are like Celeron's during Pentium 4's age.
There is absolutely no relation between Pentium4 and core2duo.
core 2 is a totally different architecture. Intel tried build upon P4's architecture and they faced lot of issues with speed, scalability, heat, power dissipation. So, they went back to blackboard and created new architecture called core microarchitecture. That is the beginning of core duo. Then came conroe microarchitecture which shifted the balance of power towards Intel. Core2duo was based on this architecture. Now, it is Penryn microarchitecture for core2duo's and Yorkfield for Core2quad.
Intel is going to release Nehalem microarchitecture on November 14th.