They were both announced yesterday, and they look great to me, especially because I have been holding out on getting a T-series one because they lack mp3 playback capability. Total size, volume-wise, should be comparable to the N series, but for all the features you get (built-in digital camera, built-in voice recorder <-- not confirmed, built-in mp3 and video playback, and 66Mhz dragon processor).
Since their color T-series have just been recently released, I would expect Sony to wait another 3 months or so before this one is brought out to the US.
If the N710/760 and T615 hadn't done so well (in fact the T615 is now the top seller PDA in several stores), then Sony, as in the past, would have abandoned the idea of bringing out the product to the US market (these toys do cost $400+); but since it's not the case, you can bet it's only a matter of weeks before we get our hands on them!