For what it's worth, I've been using the Pro version for 6-7 years, upgrading roughly every other year. If the subscription model would let you cancel and keep the latest version in perpetuity, I would be on board with a subscription. The fact that I can pay a subscription rate that basically equals what my annualized upgrade rate was, and then have to fall back to 3 versions ago if I cancel my subscription is probably a deal breaker for me.
There's little to no loyalty towards customers that have voluntarily continued to contribute dollars to the product. Make it mandatory, and we get frustrated and make do with our current version, or go looking elsewhere.