People have been saying it for years now... heck even before XP came out I heard rumblings of MS switching to a subscription-based OS model. Well it hasn't happened yet, it's not happening with Windows 7 and I can virtually guarantee it won't happen with Windows 8. So you aren't the first person I've heard this from... so I definately didn't "hear it here first".
MS would be risking a lot by radically changing their licensing model. Solidworks can afford to piss people off... Microsoft cannot. Once you open an old file in Office, for example, you can still save that file to make it compatible with an older version of Office. (You can also create new files and save them in the old format). Now, of course, if you save in the new format, then the old versions can't do a damn thing with it.
If Microsoft does switch to any sort of subscription-based model... they might do it with something like Office... but it would be a very difficult pill to swallow on the OS side. They have the overwhelming majority of market share so they can make their money on corporate licensing alone. Whether you believe it or not, MS has to keep it's customers happy... because happy customers are repeat customers.
Like I said, I'll believe the sky is falling when I see it.