Each purchase gets one year of free upgrades, but I make no guarantees about what enhancements will be coming in any upgrades or when.
Your first few enhancements seem relatively easy to add, capturing extra fields is more problematic. It would not be too difficult to add some optional fields and allow showing or hiding them and customizing labels for them but doing something like Form Wizard there is quite a different thing. I don't plan any integration between Event Calendar Pro and Form Wizard Pro, having dependencies or cross talk across features is not really feasible. Features need to be self contained and de-coupled from other features. About the only thing I can think of that would allow some kind of integration would be to customize the confirmation email for event registration and include a link to a Form Wizard page and ask the user to visit the page and provide the needed info.
Its already possible to capture some extra data from users by customizing the user profile and making some fields required for registration. A user must register to proceed to checkout so they would be prompted for any required registration info before they could checkout.
The calendar does indicate sold out events on the page and won't accept orders for sold out events. However in the case of events that may sell out quickly it can be problematic because you have no control over the timing of when someone gets redirected to paypal and when the order is confirmed by paypal so its possible to over sell if orders are coming in fast. Best to buffer a little and set the tickets available to less than actual in that case to keep a few for orders that may go over. You can simulate sold out events on the demo site to see how they are indicated. Set the tickets available to a small number and then run a few orders through.
Best,
Joe