From a big picture perspective IMO the change in system level partitioning bringing the memory controller on-chip along with CSI I/F links is major enough to warrant calling it Core 3. An improved microarchitecture with much higher performance is the icing on the cake. It's certainly a bigger change from Penryn to Nehalem than Yonah (Core Duo) to Merom (Core 2 Duo), aside from 64 bit support. OTOH it is a marketing issue so it doesn't have to make any sense or be consistent at all. ;-)
Re: I'm wondering if there are enough arch changes for Sales and Marketing to call these products Core 3.
Branding is not a technical specification. They can call it whatever they want, but IMO, it would be silly *not* to increment the brand with this design.