The notion of an Epcot overhaul should get me incredibly excited, but the GOTG rumor really gives me pause. Yes, I'm sure they could graft on some sort of lip-service to an "edutainment" concept as the framework from which to hang a GOTG coaster, but let's get real... Disney's probably not going to make that effort. It will very likely be an attraction that could otherwise be totally at home in either Tomorrowland or somewhere in Hollywood Studios, with nothing about it that makes it indelibly "Epcot."
That said, I'm coming to grips with what Epcot currently is, and what it is likely to evolve into. As long as Spaceship Earth and Living with the Land can hang on, and the World Showcase pavilions don't lose any of the attractions they already have (I'm okay with IP-based attractions in WS... provided they're additions that thematically fit), the park will continue to occupy a fond (if also somewhat bittersweet) place in my mind when I think of it.
The sad thing is that this GotG coaster concept would have been a great anchor for a superhero/action-based area in DHS (paired with the BH6 flat ride from Tokyo, the WiR concept going into MK and an Incredibles dark ride) and radically increased the amount of attractions for DHS.
Add in SWL, a Monstropolis mini-land instead of TSL, a GMR update, Muppets Courtyard, an enclosed B&TB replacement, a Little Mermaid replacement and that Mickey E-ticket replacing Launch Bay (paired with a direct path over to RnRC/Sunset) - DHS would be set for the next 10-12 years, enough time to allow the creation of a new identity for the park.
The old Epcot is no longer relevant. Its not a viable concept for the 21st century. World Showcase works. Future World does not. Disney needs to change the theme of Future World and add a couple of good new E tickets and a D ticket or two to the area. Utilizing it as a Festival park works. Nostalgia sometimes blinds us to reality.
The focus of Future World should shift from the future to a more general/timeless 'Discovery' theme IMO. But some of FW's lineup is fine (or could be fine).
Journey into Imagination's original form was definitely timeless and could have stuck around for 50+ years with updates here and there. Imagination never becomes outdated and is at the core of all discovery/innovation.
Spaceship Earth is focused more on the past, so if they stopped predicting the future at the end, it would be fairly timeless.
Living With the Land just needs working AAs and a nice update. It's fine otherwise (and the Behind the Seeds tour is fairly popular).
Nemo could easily be an engaging edutainment dark ride with a proper budget - just have Mr. Ray take Nemo, Dory and the other school fish on a tour of the oceans (Atlantic, Pacific, Indian, etc) and explain what we can learn from the seas. Turtle Talk could also return to a more education-based format of Crush answering questions about turtles, etc.
I agree on Energy - that's a concept that becomes outdated as soon as the ride premieres due to how much change there is in the field on a regular basis. Test Track, too - automobiles become outdated quickly, so it pretty much has to stay a thrill ride and avoid most edutainment.
M:S could be awe-inspiring with 4K graphics, randomization (traveling to different planets, etc) and actual interactivity (altering orbital paths, etc), paired with a second part to the attraction. Kids love outer space, so I doubt the attraction would truly become outdated since space remains fairly unexplored.
Tomorrowland is easy to fix since in the MK, a sci-fi reboot of the area wouldn't seem out of place in a park featuring mostly fictional attractions. In Epcot (a more realistic park until recent years), sci-fi would seem weird (unless GotG takes over Energy/WoL as insiders suspect).