ArxI played TFC for 8 years. I didn't like the idea of TF2. I saw a load of videos and hated that they took all the speed out of the game. Sadly I had to move to TF2 as TFC was dying and I still wanted to play a game that had some of the TFC characteristics. I feel like Overwatch is pretty much the same thing happening again. Imagine going from this to TF2: https://www.youtube.com/watch?v=hOyGGs9s2jA
I disagree with this because of exactly what you said in the rest of your post. Overwatch is more moba-like than FPS-like and I don't think that there will be enough in common for the TF2 community to migrate many players completely.