For you non Mass Effect fans out there who have been living under a rock, BioWare basically was under extreme scrutiny with the original endings to Mass Effect 3 -- many felt that they were unsatisfactory conclusions to an adventure that they spent years completing. Months later, BioWare offered free "Extended Cut" DLC, which augmented the original endings with some extra cutscenes and even added a few new endings to the mix.
Some fans were satisfied, and others thought it was too little too late. Now, the "new" endings are going to be the Wii U's default option -- meaning, the original endings effectively do not exist on the upcoming console.
As for myself, I still can't believe they're bringing Mass Effect 3 to the Wii U at all. I assume the market is already fairly saturated (who hasn't bought ME3 who didn't want it already?), and considering the first two games aren't on any Nintendo system known to man, that's even less of a market.
Mass Effect 3 Extended Ending on Disc for Wii U [Nintendo Life]