Heres what I think is gonna be announced:
Most likely scenario in my eyes:

iPod nano gets the redesign we've all been talking about, with a bump to 16 GB as the top model. Huge emphasis on the slim form factor and videos. No touch controls on this one, but I'd expect them to do something *very* interesting with the click wheel, since leaving the controls sideways while in video mode seems very sloppy, not at all like Apple. A redesigned user interface would also be necessary, maybe something more Touch-like with standard controls. Brighter colors are nice too, hope they have a deep blue one.

iPod Touch gets a minor redesign. I've always thought the plastic back on the iPhone 3G was way sexier than the old back, and much better than the shiny metal iPod backs. Some new features such as iPhone 2.1, which could mean GPS but I think is gonna be wireless music streaming (introduce it on the iPod first, to keep it separate from the iPhone and give people a reason to buy one.) They'll probably introduce a 64 GB version and drop the 8 GB version. 64 GB could be available in White?

iPod Classic doesn't really need a refresh. At this point, I'm not sure there are that many people who still want more capacity. At most, to cater to the hardcore fans, Apple is gonna bring in the 250 GB Classic, possibly drop the 80 GB since it's sharing market space with the 64 GB touch and we all know which on they'd rather have you buy.

iTunes. I think this is where the big announcement is going to come from. Considering how little we know about it, either it's gonna be nothing (visualizers...yay) or it'll be something huge. Interface redesign and bunch of new features, including Wireless music streaming and syncing. Imagine that in any location with a Wifi network (or even a 3G network) you could have access to you entire music library, not just what's synced to your iPod. Each device would store a small .lib file that contains all the music you own. Then the iTunes store could stream it to you when you have Wifi access.
It's neat, but consider the implications. It would obviously only work on songs available in the iTunes store. Eliminate all other sources of music. Closing the apple loop even further. They could charge for this service, and no doubt there would be thousands of people willing to pay or even
subscribe to this kind of thing. There's very little chance of an unlimited music subscription service from Apple, but this seems like a viable and just as profitable (the important thing) alternative. More money AND further controlling the consumer? Where does Steve Jobs sign?

The price scale is probably going to look something like this:
$149 - nano 4 GB
$199 - nano 8 GB
$249 - classic 80 GB (if it's still around)
$299 - nano 16 GB, touch 16 GB
$349 - classic 160 GB
$399 - touch 32 GB
$449 - classic 250 GB (limited production I would say)
$499 - touch 64 GB
If Apple wanted to completely monopolize the market even more than they already do, dropping everything $50 would eliminate practically all other competitors.