Atom D2500 and D2700 were launched in late Q3 2011, roughly a year ago, and in last few months the faster D2700 processor has been replaced by the slower D2550 processor that is here to stay. The 2.13 GHz Atom D2700 has officially received End of life status as listed here.
The D2550 is clocked at 1.86GHz, just like the D2500, but the one bit a bigger number has two cores and four threads while the D2500 has two cores and two tread support. That is the main difference with an exception that D2550 sells for $47 while D2500 goes for $42 suggested retail price.
Intel doesn’t plan to change the D2550 and D2500 at least until end of Q3 2013 which is roughly a year from now and these 32nm desktop Atoms will have to do. This sounds like quite a long time without any innovation in the Atom market, but Intel probably has a feeling that this marketing is not something that will continue to grow.
In addition, it has introduced Intel Celeron BGA parts based on Sandy Bridge simply called 847 and 807 that will be more than sufficient to run Windows 8.