I was at Disneyland yesterday and I was also surprised to see the amount of vertical progress as well.
I suppose my major reservation is that no matter how quickly they finish it, this needs to be a really, really good ride to balance out the general aggressively mid nature of Avengers Campus (and Mission Breakout was pre-existing so it doesn't count). It's telling that on a very busy Saturday the posted wait for Webslingers was 30% of Mission Breakout overlay (25 minutes vs 75 minutes). It's just a ride I walk by every time I'm there, and think, "I'm not interested in that."
At the end of the day, I just want to have a new original ride that compels me to re-ride it, and if that takes three years, I'm fine with that.