To really answer the original question, yes, there is at least a little bit of information that real ISO images to install WILL be available, so with a proper license, I am (still) assuming that you could set up a dual boot (tripple?) situation. The license is the tricky part (as mentioned above), since it is the activation and licensing that is tied to the single machines "fingerprint".
Maybe, if you cloned your existing Win7 (or 8.1) to a VHD, and ran it "virtually", you could do something else to bypass the intended licensing...
As for upgrading from XP, the issue would be more of any "in place" process would be a bit "iffy" at best, and since MS is basing all of the "activation" on the existing fingerprints it has tucked away on it's servers, it is unlikely that any sort of a "hack" can be implemented to get a "legit" copy...
Of course, I'm fairly certain that non-legit means will eventually exist...
Scott.
P.s. Hope everyone is having a great summer!