I'd agree that it's probably not meant to be the same person, unless there's something really strange going on here, because Nords just don't live that long, under normal circumstances. It's probably just a different person who happens to have the same name, though it's certainly not impossible that it's intentional, though if it is, I'd say it's more likely that Skyrim is referencing Oblivion rather than the opposite, since while Bethesda may have been making plans for Skyrim at that time, I doubt that the name of your mentor was the first thing they had thought out. And when you hint at future games in the current game, you're probably going to be hinting at events in the story, like how Morrowind suggested there would be problems with the succession and had that cult talking about Daedra invading (While things might not have turned out the same way as players might have initially expected in Oblivion, I highly doubt its a coincedence that these themes later played a part in Oblivion.) and there were some rumors of troubles related to Skyrim in Oblivion as well, though none mentioned anything about the dragons, and the one that seems most related to the story of the game is probably the one I think I heard about the Greybeards talking about the end of the world or something to that effect, and now we suddenly have a prophecy about Alduin returning to destroy the world, although the Elder Scrolls V could have been set in pretty much any province if we go by the rumors in Oblivion, as lots of provinces were having troubles, but back to Esbern, calling a character Esbern wouldn't even constitute as foreshadowing as no one is going to think, upon seeing a character with that name, that it's the name of someone you'll meet in the next game. Foreshadowing would be giving you some actual concrete hint about events that will happen later. It wouldn't explicitly tell you what's going to happen, that's what we call "spoiling", but it would give you enough that you might be able to start speculating on what will eventually happen. Giving us the name of Esbern hardly counts as that.
They started planning right after Oblivion, and possibly came up with the basic concept even sooner (which would fit with M'Aiq's dragon comment too).
M'aiq commented on dragons in Morrowind too, though.