Sorry for the essay in advance.
As a Southern California local, I have ridden ToT in its current, Twilight Zone, theme. I love the idea and the queue is my favorite part of the current experience. As for the GoG retheme, I'm torn.
On one hand, the huge Marvel fan in me is excited for a new land themed to my favorite heroes. The prospect of a possible E-Ticket attraction joining Radiator Springs Racers in this new land is what I am most looking forward to. Having not had an innovative attraction at the resort in over 20 years (Indy), I have been waiting for an E-Ticket for a while.
Then, there is the fact of doubling-back by Disney. Yes, the California theme of the park was originally a total failure (mainly due to off-the-shelf rides and gaudy decorations), but the recent renovations have turned the park into a beautiful piece of mastery. Having taken a trip there alone back in March, I found myself wandering around Grizzly Peak and Carsland, forgetting I was in a theme park and not in the "real" world. But this announcement tells me I might be alone in these feelings.
Obviously the major renovation that finished back in 2012 has not reached the general public the way Disney expected. On that same March visit I noticed DCA felt about half as full as DL did. ToT only had a 10 minute wait, Screamin' boasted a lofty 20 minute wait, and Radiator Springs Racers was the longest at 45 minutes. All these were smack in the middle of spring break, one of the parks' busiest times.
In short, the retheme would be a brilliant move by Imagineering if it had not committed to the "California of the 20's" theme less than 5 years ago. Now, I would not be surprised if the name is changed to "Disney Anything Goes Adventure" in the near future. I loved the idea of Star Wars Land, especially since it was replacing a scarcely crowded corner of the park, and now this "Marvel Land" announcement has made me even more excited for the possibilities of attractions both of these expansions hold.