It is looking more and more likely that there will be movie rentals on iTunes. Frankly it has to be done, the real money makers for movies is not sales but rentals. I have yet to buy a movie on iTunes (though I have bought a number of TV shows), and rent all my movies on Netflix.
If Apple does offer movies on iTunes, I would certainly start renting them there.
There are two caveats to bear in mind though:
First, I tend to watch movies in the long tail and eschew most of what hollywood puts out. Netflix does a very good job of covering this long tail.
Second, and Om Malik touches on that in his post about this, the quality of the video is pretty poor and needs to improve for the experience to be good. Of course I understand that there is a tension between quality and file size, but this is where H.264 should shine (or so Steve Jobs told us).
Updated – Paul Thurrott also talks about this.