Evil Alpaca said:
Unless Bioware wants to declare one ending canon...
You can't make a Mass Effect sequel that takes place after the third game, regardless which ending you pick. In all possible outcomes, the entire Mass Relay network was destroyed. It's not the same world anymore. What used to take hours/days of travel now takes decades or centuries.
It would take millennia for them to replace the network; each relay needs to be linked with a corresponding partner. That means building these blasted things from scratch, then fly over to the desired target location and build one there as well. Of course, to cut time, Earth and say... Palaven could coordinate to build linking relays on each others end, thus negating the need to fly between the places during construction but that requires them being able to communicate with each other. So lets assume the various homeworlds can talk to each other with these newfangled quantum entanglement communications arrays, and speed up the rebuild, there's yet another snag in that plan. The difficulty to build these relays.
Each relay is 15 kilometers long, is made out of unknown materials and requires wast amount of element zero. The stupid council never even bothered studying the relays with the intent of learning how to build one and now they're all gone. The only possible relay that might still exist is the Conduit on Ilos, which was an experimental miniature version, built by the Protheans and not part of the original network. Its corresponding partner was inside the citadel, before that blew up and it's entirely possible that it also was affected by that choose-your-color-explosion. Of course, someone needs to fly over to that planet to check if it's still there, which would have taken decades, from the nearest relay.
This of course is just one of the many things that people, that actually cared about the story, were complaining about when they were bitching about the ending. Any way you slice it, if you want to see a sequel that allows you to travel the galaxy and interact with the various worlds/races, it either needs to be set really far in the future or before Shepards saga. If taking the far in the future route, Bioware would also have to pick one of the endings, like you said, since the various choices had the potential of changing how the universe worked in rather radical ways.
At any rate, I really don't feel the slightest inkling of a desire to get it. Bioware really needs to work their butt off to sell me the concept of any future releases, before I can even consider buying it.