Well, I think it's fair. If there was no subscription model, this would be the same as buying the version that was available at the time of your purchase. Everything that gets released after that is only a teaser that nags you to continue your subscription. You don't need to update.
Before the licensing change if you purchased a major version such as 5.0 you would get all upgrades for free until 6.0. This was the change that caused the uproar because that was no longer the case.
