These older NetBurst based CPUs, particularly the Pentium Ds, were merely a way for Intel to hasten their entry into certain markets, such as dual-core desktop CPUs. Performance, while better than older architectures, wasn't anything to be impressed by and neither was their power envelope. I'm actually surprised Intel didn't begin this process months ago, though apparently there is still some demand for certain units in the market currently:
Only some Pentium 4 6x1 and Pentium 4 5x1 processor may fall under the special discontinue program, because they may still be demanded by the OEMs and system integrators. As for all other Pentium 4 and Pentium D processors, the last orders will be accepted on December 7 2007.
The series won't be missed, with its younger cousin Core 2 taking all the glory.