Well, the current model (explorer 8000) was pushed back 2 different times - i.e. it was due in January for beta, but didn't start testing until February and was set to go gold in March but didn't until April.
So, IF beta stars in January (and only beta testers will have the early boxes), I would expect it to become available to the general public 1-2 months after that. I would be surprised if you could pick it up at your cable store (the last stage which happens once a box has good supply and is deemed "stable) before the end of March. Understand, this is totally a guess on my part based on experience with other boxes (Exp. 8000, Pioneer HD, SA HD, ect).
As far as becoming a beta tester, they usually have a fairly small group just because it isn't a situation where there are many different configurations like there is in the pc world (roadrunner had a large group of "earlybirds"). You pretty much have cable in, and one of 4 or 5 configurations for source out. This means it is very difficult to get an early box as a beta tester.
How about one more teaser? I had asked about the drive size (80 or 160 GB depending on the Cableco) my buddy said the following:
The S/A answer for storage is external 1394 boxes
I realize that currently the firewire ports are inactive, but this does give me hope. Imagine slapping a firewire box that accepts normal hard drives next to your 8000HD. You could have a drive that you archived Football on, one for . . . well, what else is there? :-)
Anyway, it may or may not happen, but the fact that SA thinks that way excites me.
Ok, ONE more teaser.
Multi-Room should show up in 04 Q1--2 also.