Not likely -- the same applications available for Mac OS X now will be available in the future.
When programming for the Macintosh, you mostly use APIs that are native to the operating system and independent of the processor architecture. That means that many peograms will only have to be changed ever so slightly to run on the Intel version of Mac OS X, which means that the operating system itself really isn't that much different.
Short answer: it's not going to make programming or porting to the Macintosh any easier, and applications that are Windows-only now will not suddenly become Macintosh-compatible, nor does it mean that Macintosh-compatible versions will be considered.
To the end user, the switch will be pretty transparent.