Let just think about this a bit. First MS has not even pulled a slim or even a real price cut. Only in Japan is the PS3 really kicking the 360 butt which everyone pretty much expected. The 360 has sold pretty strong in NA and continue to hold off the PS3 even with some of it's bigger guns hitting the holiday.
The 360 has some very nice exclusives that cover a wide range of genres.
Personally I believe Sony has shown their hand early and they had to. The brought out the slim and a 100 price cut. This killed the profitability that the slim was going to bring to Sony, so I highly doubt you will see another price cut from Sony this year and probably not even next year.
On the other hand, MS has not pulled their price cut. They also have the option of a slim redesign and upgrade of the 360 (sans blu-ray). Also there is the rumor of MS licensing out the 360 arch to other companies like Toshiba and cable IPTV companies like AT&T. A licensed company like Toshiba could bundle the 360 with a blu-ray player.
I can see if MS is feeling big pressure from Sony that they could do a Slim, cut the Arcade to 150 or even 99(wow), bring out Natal and have 3 hit combo with Halo Reach for the holidays.
I certainly do not see any major moves beside games from Sony this year. 3D games sounds awesome but if it means you have to buy another HDTV set, you can forget about any real update.