I do not think the 7 SLIC will change, then again the product is not final so I do not know. However though that does not mean that the OEM is obligated to give the older media nor the means to activate it.
I do not know either, and it is one of the arguments i didn't want to get into because windows 7 is not final we will never know until it goes to RTM i was just expressing my thoughts, for myselfe i have a dell inspiron 530 and i can install xp or vista with correct oem bios files or certificate and serial number for vista. This model is still quite a popular machine and hopefully when windows 7 comes out dell will still be doing it. So you will have the option of having windows 7 , or vista. that should be in the bios.
Apart from the license/activation issue when downgrading, there is another issue that hasn't been adressed anywhere (that I have read anyways). For newer model machines, especially laptops, that come with a new OS, the OEM (HP, Dell, etc) rarely ever releases drivers that are compatible with an older OS than what was pre-installed. In other words, if you buy a brand new laptop with Win7, you may be allowed by MS to downgrade to WinXP, but if the OEM doesn't provide XP versions of the drivers (for custom keys, wireless cards, embedded video, Blu-ray burners, etc) then you likely will be wasting your time trying to downgrade. I'm pretty sure I've already read about people that have had problems downgrading from Vista to XP because the vendor didn't supply drivers for XP. The challenge will likely be even more difficult with people trying to go from Win7 to XP.
Yes you are right, which I think is wrong, but there are a lot of drivers out there so a lot of times people complain there are no drivers but the truth is that they have not looked hard enough. That being said though not everybody out there in internet land knows how to check hardware by Vendor ID and PCI Device ID, so this can lead to people not finding drivers for things. Other times there are no drivers because it is up to the ISVs to put out drivers for their products, and they do not want to. I seem to remember an issue with a built in webcam on some HP laptops not working.