This is pure speculations but I expect the speed to stay about the same. The software may be optimized with future versions but more stuff (features, visual things) will be added so it will probably cancel out. I can say that this is my experience with Windows OS updates. Don't have a Mac but maybe someone else can comment.

I used to be firmly in the pro flash camp (because I liked making mini games with flash, it's pretty easy!) but now I am tending towards the middle. Many restaurant websites use flash so I have found myself not being able to look at the menus, and going to my laptop. On the other hand. I read the NY times online, and every time I do, this huge flash ad pops up, which is annoying. When I started paying more attention to it, really a lot of ads use flash, and not having flash support gets around them...