I think it'll stop with the Cell Phone. From there Apple will continue to tweak and fiddle to get things to work with each other as best as possible whilst still adding new feature as applicable. There really isn't much of a reason for Apple to make other devices past what they are making. Personally, I don't even think they should be making the iTV, but I think it will still succeed and when it does it will greatly help Apple's image and brand.
Just as long as their computers don't get overshadowed(they already are somewhat, but it's not too bad)
I suppose Apple could expand their Cell Phone to become a line of Cell Phones, from a fairly basic one(with no screen
to a fully functional PDA smart phone type one. But I don't see what other 'consumer devices' they'd be interested in.