I think that 360 could possibly pick up but not until later in the year. While MGS4 did see a dropoff this week I believe it will still carry some momentum especially with new shipments of 80gb bundles. (Which I might add was a very good move by Sony.)
Microsoft has a pretty good lineup for the 2nd half of this year especially in Q4. However a lot will depend on the timing of a price-cut and the success of major titles on both the PS3 and 360 (and of course E3). The MMOs that will be released on the 360 should also move a few consoles since some of them like Age of Conan require a high-end rig to play and it would be cheaper to play them on the 360 even if you don't already have them.
For now Sony has the momentum and it's possible that MS could take it back for a bit but I think Sony will eventually edge out the 360 in Hardware sales by the end of this generation or sooner. (profit and software remain up for grabs though) Btw I am not Sony's biggest fan by any means but hats off to them for the success of MGS4 and the bundle 








