I feel ya... I too will be getting it for the 360 and im pretty sure all current gen games will drop dramatically in players come the launch of the new consoles. As to there not being a single player story, I feel some games need to focus strictly on multiplayer to flesh the experience out as much as possible, though it would be interesting to see where they would take this if it were a story...
It seems that they have a semblance of a story in their game right now with how the game gets set up. The problem is I don't know how developed it is going to be. To me it just seems like it is something that is tacked on. I want to care about why they are fighting, not just fight for fightings sake.
Take Battlefield 2142 for instance. It had fantastic gameplay. Massive 64 person games with Titan Mode. One of the best shooters I have ever played. Yet the only real explanation given was at the title screen vid as well as a few paragraphs of text on a loading screen. Most of which was completely meaningless. There was no investment for the player. No motivation beyond just shooting things and hanging out with friends online.
I find that games are far better when the player has something invested emotionally with the characters. Be it from single player or their online avatar. Halo and CoD do this amazingly well to be honest. The single player has characters in it that people focus on. They get a reason for why there is a war on. Why these people/things exist and why they hell they are way out in space to begin with, or in CoD's case where ever the hell those games take place on Earth. That perspective, the emotional attachment, transfers over to multiplayer even if only slightly. I see players customizing their characters to suit their personalities as well as ways to fit into the story from either of those games. The maps are out of the story as well. Or at least resemble sections of the story where you can relate to them. They have meaning to the player instead of just some random rubble strewn area or pile of rocks that nobody give a damn about.
Yes that is my honest opinion on that matter. Take it or leave it.
So far Titanfall seems to have a story to it, but only just. I really hope they spent a significant amount of time on it to flesh it out and make the characters, places, battles have meaning to a player instead of just the grey mush that shooters are becoming. A single player campaign could easily do this, what they have now could possibly do this as well but I am uneasy about it. I only hope that it gets fleshed out so it is actually significant.