Yes, and we have been for a while. But as you can imagine, you can't stop adding features to your existing product and expect to survive. 1M lines of code isn't something you can port quickly.
Is there some sort of process in place for mitigating the potential "1 step forward, 2 steps back" path of adding features in ActionScript and then having to eventually port them?
Where we could, we certainly tried to avoid it. The bigger problem is just the opportunity cost with regards to resources involved with the transition.
Which is a large cost no question. Especially with the size of the codebase you mentioned. What I'm interested in is how, if at all, the transition process is managed. YouTube's transition from Flash might be an example of this. They managed it by creating an opt in sort of beta experience that they tested for a long time before making it the default.
Another thing I'd be curious about is the line at which the opportunity cost of not making the transition surpasses the cost of not developing new Flash features.
On the other hand, Google has the advantage that it's a web/programming/tech company at heart. So when a CEO hears that Steve Jobs is not allowing Flash on the iPhone (and when a branch of the company helps develop HTML5), he sees the writing on the wall and is willing to work on migrating to HTML5.
When a bank CEO, who has no idea about anything except "Well Adobe is a big company and I've never heard anything about this W3C, and how long will it take? How much will I make off it right now?" hears (if he even does) that Apple doesn't like flash, he won't care.
