By the end of this year you can expect a T5500 running at 1.66GHz for $209, but the rest of the new models won't appear until next year. In Q1 2007 Intel will introduce the first Low Voltage Core 2 Duo processors, the L7400 and L7200 at 1.5GHz and 1.33GHz respectively. In Q2 2007, Intel will introduce all of the 800MHz FSB Core 2 Duo parts, as well as the Ultra Low Voltage Core 2 Duo U7500.
The difference between the T5500P and the T5500 is that the former is a Socket-P part (Santa Rosa platform), while the latter is Socket-M (Napa platform).