I would gladly pay, but tying things to a yearly/bi-yearly deal is always a gamble, because should the project end at some point (and it can happen to any project), the end user is left having paid for something he can no longer get the agreed upon updates for.
Here is my thought:
Construct 2 Free - Fully functional but with splash screens and no exporters can be used except for .exe's, no special plug-ins, no updates. Barebones.
Construct 2 Silver - Fully functional, no splash screens. Only .exe's can be exported, only a few essential special plug-ins, updates must be paid for.
Construct 2 Gold Pro - Fully functional, no splash screens, .exe exporter, more essential plug-ins, choice of one major exporter (xna, iphone, etc.), all updates included for the life of the product.
Construct 2 Platinum Pro - Fully functional, no splash screens, all plug-ins, all exporters, all updates for the life of the product.
Construct 2 Custom - Customization is big, and this one would allow us to customize exactly what we want thus determining the final price the we would pay. The minimum would be above Silver, but lower than Gold Pro and Platinum Pro, and as we add things one-by-one we would be able to see the price climb in real-time.
Notice I used the words "life of the product". In order to move developers forward into the future and be able to offer totally new versions of Construct to justify a new purchase, you'd at some point end production and updating on Construct 2 Free, Silver, Gold, and Platinum, and begin a new cycle with Construct 3 Free, Silver, Gold and Platinum... and then 4 and 5 and so on, much in the same way that console dev kits are handled from one generation to the next (i.e. development of new tools and updates on those kits cease, and developers have to pay to move over to the new kit).