in my point of view Fallout is the best example. It was an Turnbased, isometiric, non-openworld Game and turned into a 1st/3rd Person, shooter openworld and it got success - especially on the console -, but for me as the old Fallout guy it was feeling not right and the core of the game was gone forever. Thanks to Wasteland2 and can kind of get back the Original Feeling.
I totally agree to Frenzy-kun, it will brake up the fan base, but with regards to Fallout that does not mean it will not have Success!
So Larian, what will you do now?