I think you're right. It definiately looks like a crossover title. Especially since each game's respective website has the same apocolyptic sound bite playing in the background. I'm sure Red Storm would not do this if they weren't connected in any way. Sounds like a great idea.
But if it takes place 20 years in the future, won't Sam Fisher be like 65-70 years old? Seems a tad old to be going on a political thrill ride. But hey, if the geriatric Indiana Jones can go on another adventure, I guess Sam can too.