I think that would be harder for MS second time around. Due to their desire to get Blu-Ray out plus their current position with PS2 close of cycle Sony had no choice but to let MS release well before them.
Unless the PS4 gets caught the same way, with something new vs MS console being built on less restrictive (initially) technology, I think Sony would most likely make sure they can release much closer to MS.
After this gen, unless they are really dumb, they will make sure that they can respond quickly to any MS console release.
Try to be reasonable... its easier than you think...