I hold judgement until M$ actually releases something.
Current rumors suggest everything from no "legacy support," to a 128 bit OS (yeah, they haven't even really gotten out of 32). Rumors of something from M$ generally snowball into insanity well before the product is released.
Speaking as someone who liked longhorn, before he experienced the fail that was vista, M$ can turn into crap or gold relatively easy. Given that they're introducing windows 8 specific ARM processors (read, mobile processors), this is likely not a full desktop roll-out.
In two years I can see a completely new OS. For the time being, M$ can't even remove the remnants of XP. Switching to yet another desktop OS doesn't make fiscal sense.
Here's hoping that M$ actually learned from their most recent failures, and will release two decent OSs in a row. A little bit of competition from the fruit and Linux hopefully is pushing them towards something amazing.