If it isn't search or video, Google always has one foot out the door.
I believe that one of the reasons the stadia failed is everybody knew about the Google graveyard and wasn't willing to buy into an ecosystem destined to die.
I wouldn't be surprised to find that this is also something that would affect their ability to attract good talent. People want to feel like they're working on something meaningful that's going to stick around for a while. Putting years of your life into developing something for Google just to have it hit the Google graveyard has got to be deeply dissatisfying.