The speculation from my general area is that Apple will never (never say never, right..) make a DVR. It's not in their interest to make a DVR. There are several companies that are doing the DVR thing for Macs (el gato and Migila) and IMO, Apple shouldn't tread those waters.
As for a Tivo killer, there's too much going against it for Apple to do. First of all, to do a DVR right, it's going to cost the end user a ton of money. The Tivo Series 3 will cost $800 (less with rebates) plus the monthly fees. Tivo's going to have a tough time convincing people to buy the S3 when the cablecos have an option available for $10/month.
Here's what I would like Apple to do. Open up Front Row so that companies like el gato can integrate their eyeTV software into the Front Row system. That way, I can have a Mac sitting in the office with an eyeTV box to record HD programming off of cable. Then, I could have an iTV in my living room to play the recorded material onto my 46" LCD HDTV (which I haven't bought yet).
If I want, I could initiate a purchase of a movie from iTMS (provided the quality of the movies are good) from the iTV itself so that it downloads onto the Mac in the office. A rental plan would be even better. That way, I could completely isolate myself from the real world.
ft