But Xbox 360s or Playstation 3s don't just vanish into thin air when people buy a new console, from either company. My 360 and PS3 sit quite happily alongside my Xbox One and PC. People can still play their games.
The Mass Effect trilogy runs on the Unreal Engine so a HD upscale wouldn't be difficult. As I said though, is it worth the effort for the money they'd get. You see a huge demand for it, I don't. At the moment EA seem to agree with me.
Given the popularity of trade-in credit programs at most game retailers, and just anecdotally speaking, an awful lot of people trade in their old consoles towards new ones. Your 360 sits next to your Xbox One, but for plenty of people that is not the case.
I guess your penultimate sentence sums it up, though: I do see a sizable demand. From first-time players, from players who would find hooking up their old consoles tedious, or from players who no longer have the games (or a console to play them on) but would like to revisit the series prior to ME4.
FWIW, "sizable" is not synonymous with sufficient. I said a lot of people would buy a remaster, and I stand by that assertion. I also said the real question is the development cost (what it costs to do it) and the opportunity cost (what they could be devoting employees and money to instead). If EA opts not to do a remaster, it's not necessarily because they agree there's not a huge demand. It could just as easily be because there's an even huger cost than that demand warrants.
Full disclosure: I've never played an ME game, and I have firmly moved into the current console generation, meaning I likely will not be playing the first three games unless they are brought to the PS4 in some fashion. I would much rather approach ME4 having already played the trilogy, but it does indeed seem like EA has no intention of making that happen.