There are games this gen that didn't hit break even at 5m sales - Red Dead Redemption, GTAV and GTAVI.
I would imagine it's true for games like Destiny that anything below 5m will be considered a failure and really they're expecting to hit the 10m+ mark. Destiny is a bit of an exception as Activision really only put all of nothing into their launches, and they're putting absolutely everything behind that game, but still once one publisher starts to play this big budget gambling game it won't be long until others are forced to join.
One expense that's exploded you forgot about is marketing - in the NES / SNES era games had adverts but it wasn't really a big thing. Marketing budgets today can far exceed development budgets (I think COD:MW2 was over $200m) - and that can quickly turn a break even point well beyond the 5m market let alone 1m. I think developement budgets are going to somewhat plateau this gen - with easier hardware to develope on and no real 'rise' in resolution - but marketing is gonna go up up up.