Well, some analysts are concerned about Disney's spending, given the number of high capex projects recently completed, and in the pipeline.
Marvel, to be clear, wasn't just a long term investment (like Carsland), but an acquisition of a profitable/popular collection of properties. If Disney doesn't like what Marvel is doing for them, they could sell it, as opposed to 12-acre lot with half a Carsland. A lot of people thought the deal was good from day one, and they've been proven right. Similarly, the Pixar deal came after Disney had made tons of money distributing PIxar films, not a big shock to the system as it solved the problem of the expiration of Pixar and Disney's prior deal.
Building a Carsland, in addition to Avatarland and Shanghai, could worry some analysts/institutionals who would forsee a longer, and less certain, return on investment. So, yes, people could get upset if they see too much construction—even construction of attractions/lands that would be popular as it would take a while for the company to earn back a profit on the investment.
Look at what happened with Disneyland Paris and all of the negatives that happened to the stateside parks after that.