I have used the x3000 for about 3 weeks now, spending plenty of time adjusting and tweaking the settings to my liking. I believe this to be crucial to get the most out of any TV. Having spend plenty of time trying out different settings, including the 100Hz option, I personally found that using 100Hz at high setting is best for Video Graphics, ie PC/Xbox games, whereas for HD content(720P+ recorded movies etc) it best left off as otherwise it looks like you are watching the movie as if it was recorded by a camcorder, not worse quality though, but it looks more like a news broadcast or a sitcom (I believe most sitcoms are recorded more then 24frames). So I would agree that it is best left off with HD content, for analogue stuff I found that I got better results using 100Hz at standard settings. In the end, the more you can tweak the setting of a TV, the more likely you will adjust the picture to your personal liking and the Sony has plenty of options you can tweak.
Going back to Crysis, apart from upgrading my TV over Xmas I also purchased a MSI 8800GTS 730Mhz model, upgrading from my 2 year old, iirc, ATI X1900XTX. I just ran Crysis benchmark at 1920x1200, everything High, No AA, 3 loops, I got 29.77 fps. But the most interesting test is running clone mode, so desktop is showing on both Sony and Dell, running Crysis Benchmark at 1920x1080, All High, No AA, 3 loops. On the first run I switched off the 100Hz on the Sony and viewing both the Dell and Sony it looked identical, but on the 2nd run I switched the 100Hz to high and it really show a big difference, much better and smoother imo. I know the 100Hz is more like 'visual trickery', it is not physically making games run smoother or faster, but from a visual perspective, ie. what you see on the screen (which is really what matter anyways), it simply looks better, so I would say, 100Hz on the Sony is deffo worth the extra money. Also another very useful option for gaming, I found that the option called 'Detail Enhancer' also makes a positive impact on the viewing pleasure of gaming, making, esp distant object, looks much clearer.
As for new models coming out, not 100% sure but I do recollect that the X3000-x3500 will the top of the Sony range at least till end of 2008/start of 2009. I do not think they will be superceded by May-June, but I could be wrong.
Cheers.