I predict the X360 has peaked either last or or this year and will not sell better from now on. This is it's 4th year out, it's quite surprising it sold as good as it did for this long.
I dought any price cuts from Microsoft will do anything, a little bump, back to normal it's already at $199 and they come out with a price cut every 6 months - year. I highly dought Natal will do anything, just reminds me of the Eyetoy on the PS2, it never really took off, and was only accepted by a specific group of people. Other then that all Microsoft has is Gears of war and Halo, but everyone that wants to play those games already owns a X360, so that'll just satisfy the people that already own the X360 instead of actually attracting new consumers.
Microsoft needs to invest all that money into new IPs.
So I say the PS3 will continue to outsell the X360 on a regular basis (excludng the odd week the X360 will outsell the PS3 from price cut/game etc) until this gen is over (both companies stop the PS3 and X360).