Care to name them?
Once MS releases an ARM version, devs will be all over it.
The only single reason it wouldn't happen would be licensing restrictions from MS.
Can't happen:
1. Licensing restriction as you stated: serious roadblock that basically means the idea is DOA.
2. HP is not interested in producing a niche product FOR users of a niche product that they've already killed as expediently as possible.
3. The hardware is, by definition, very weak compared to what will be used to run full Windows 8 (the real deal, not WoA)
4. While you might (in theory) be capable of running WoA, it will need numerous drivers written to run on Touchpad HW - which would be HP's job, so is unlikely (see #1-3)
5. How much luck have people had with "jailbreaking" or hacking WebOS? (Admittedly I don't know much about this.) It's likely that the TouchPad itself could prove difficult to circumvent if one were to unofficially "jailbreak" W8 onto it.
Won't happen:
1. Windows on ARM is not going to provide anyone with a smart, polished, or economically-viable experience for close to a year, if at all. When Windows 8 launches, BELIEVE ME, everyone will want the "real deal"-- or they'll be waiting for the "service pack" that makes WoA a solid performer. At that point, it will be many years since the Touchpad came and went. (I think the inability to use Windows apps is going to confuse the **** out of people who own Windows 8 laptops which "behave" the same as their tablets.)
2. There is absolutely no financial reason for HP to do this: they want to sell new hardware!
3. HP's product line (and goals) are already incredibly complex, and they already have a lot of work ahead of them: they are not and have never been interested in backwards compatibility (how many kinds of ink do they make? how many different models?). Ideologically, this is just something HP doesn't do, even when/if it MIGHT make them money.