That isn't the same thing at all.

If I buy version 2 then it's mine and I can continue to use it for as long as I want, if I'm happy with the feature set. I can ignore version 3 or choose to buy it. If I buy it then I now own two products instead of one. Sometimes the older version might even be better (e.g. features I like have been removed or made worse).

With a subscription model I'm forced to pay again and again even if I'm perfectly happy with version 2.