To the people that only want the C3 they can purchase one time by $99 and use it always, they will have lifetime bug fixes but only 1 year of free updates/improvements.
So people will enjoy the new C3 version with one year of great upgrades for only one payment. Some people not needs much more, like people is doing games only for fun, as hobby or even sell some small games or whatever.(That well, they can still doing that with C2).
In case there is some features and improvements that are added that gives to a developer a good reason to update the product they can decide to pay again $99 and enjoy of all the previous updates until now and 1 year forward.
With this people with non-profit/hobby,etc... expectations that want the new version can afford that, and for the more advanced developers that needs the last updates they can pay the subscription each year to be updated.
What you think? is possible Tom Ashley ?