Looks like this afternoon's presentation should be fairly interesting. Whilst it looks pretty certain that there will be full-length movie downloads from iTunes, the interesting speculation on whether there will be anything else (hardware or software) relating to multi-media downloads. My money is on a beefed up version of Front Row, installed on all new Macs with the subtext of positioning a Mac Mini as a home theatre device (but without explicitly calling it that). I doubt that there will be any TV-related items directly; Elgato already has that covered, not to mention the differing broadcast codings and the fact that in the next few years, the transmission of TV is going digital anyway.
I also can't see a hardware video streamer being created; after all, the Mac doesn't have any concept of remote display (even though it used to under Nextstep -- sob) so it's not clear how it would even be used. And you'd need a reasonably beefy video card or CPU to do decoding, which means you'd also need memory; basically, it would be a small network computer (or a Mac Mini without a hard-drive). Making a mini smaller and hard-drive-less doesn't seem like a practical option to me; however, the airport express is just decoding MP3 and sending it out to an audio stream, which is a lot less work. (Also; MP3s are pretty much at the limit of what they'll need to be for ever -- but movies are going HD, which requires a lot beefier network and video card.)
As much as I would like an iPhone, I doubt that that is likely for this event, though perhaps sometime in the next 12-18 months. It's possible that there will be a stepping-stone device (such as an all touch-screen iPod to enable for widescreen movie viewing) and that an iPhone will take the same form factor in the future. Just look out for any built-in microphone slots, which will give a strong clue that an iPhone can't be far behind.
The next obvious question is how they'll link the iPhone. It's quite likely to work on quad-band, seeing as these things everywhere now, but the market at the moment means that operators end up customising the handsets to have logos or other built-in stuff on them (or to hobble a phone's capabilities). I think that there will have to be a lot more negotiation to get an iPhone working; quality (e.g. call quality as well as functionality) are likely to be important. I also can't see Apple running a mobile phone company; though a MVNO might work, I think it would be too outside of their core competencies to get right, especially from an investor's point of view. But at some point, I think there is room for one more big player (Google? Amazon? Apple?) to provide a decent mobile device that can also let you surf the web without hideous data bandwidth charges, and one that works seamlessly in conjunction with a wireless network back at home.
Anyway, at least Steve should look more relaxed this time. Let's see what happens at the announcement...