The "Save Toad" movement is the closest the WDW fan community ever got to an organized, on-message protest regrding the change of an attraction. One that even received media coverage.
It did nothing to change the outcome of the ride.
Disney's current goal in the theme park business is to turn the resorts into distribution channels for their collective IPs, while maintaining quarterly growth by managing the costs of new additions and current expenses that may or may not have direct lines of revenue (like shows). Unless you can convince Disney that changing ToT is not in their best interest for these reasons (without getting into legal trouble for making suggestions without being under the employ of the company), than I don't see a change in the ride's outcome unless the company comes to these conclusions on its own.
Disney will do whatever they want. Period. While telling Disney directly why you are cancelling future trips to their Florida resort is the most effective way to get your point across*, the odds of there being enough mommentum from the fan community alone to reverse this kind of decision is incredibly small. The only time Disney ever really fixes a problem like that is when it fails upon arrival with more or less everyone who sees it, like Light Magic or DCA 1.0. That might happen, but there's no way to know until it's [if it's] done. And even then, there are plenty of individuals (self-identified fans or not) who would love to see the GotG characters put in the attraction.
*There's also the question of "how big is the boycott?". Is it just WDW? Do I have to skip seeing GotG 2 in theaters or Netflix? Do I have to never watch anything on ABC again? What if I buy a one-day, one-park ticket to DLR and skip DCA?
