We'll see. I imagine there has been a pretty overwhelmingly negative response to this possibility, so that should make MS and Sony stop and think. The sad fact is though, who says this wouldn't extend onto PC as well?

There was an overhwelmingly negative response to paid online too. And dashboard ads. And Sony removing features with a forced update (Linux support removal).
The console companies do not care. They know that most of their audience isn't willing to go PC and that most of them aren't willing to go all Nintendo either.
Your probably right, which is pretty sad

But I would hope they don't do it. Besides I'm thinking about getting a gaming PC anyway, just for mods and better visuals. I hope PC games don't do this.
PC gamers are a lot more serious about "oh no you didn't" with big companies than console players. When there's a backlash with them it means terrible sales compared to the expected numbers. Just look at Dragon Age II, Modern Warfare 2, or Crysis 2. PC gamers hated every one of these games vehemently and they vastly undersold the previous games in their franchises. Piracy helps with that. IMO it's actually a positive effect, stopping games that, for whatever major reason, do not deserve to turn profit from becoming successful. Piracy as a whole would probably be healthy for the industry if more pirates restricting their YARRRGH ways to deserving titles like those three (albeit Crysis 2 left the list with their major PC patch). I doubt a big in-game ads thing would take off on PC, just like paid multiplayer failed when PC gamers refused to buy Halo 2 or any of the other early GFWL games.
Hell, Steam has "dashboard ads" in the sense that it opens to the store by default, but you can turn this off completely in the options along with any other form of "advertising." I can't imagine Valve doing a complete 180 and pushing in-game ads.
Anyway, my stance on in-game ads is thus: put them in sensible places and make them sensible products. Realistically placed and sized Coke billboard in a modern or near future city? No problem. Loading screens, the whole world only drinking Coke, or any other nastiness = not playing it.