I bet there will be, cause I definitely didn't think there would be a Portal 2 based on how the ending turned out; But still, one came.
So in my opinion, I think so. :D
(granted, if it did, it won't be for a long time.)
There is going to be Assasins Creed: Revelations, it's going to wrap Ezio's storyline. I think it's going to be late in Ezio's life because on the cover of a magazine doing a review of it, he looks very old.
And as of another story all together, I sincerely hope they keep this going to another story in the Assassin's Creed saga. I know they definitely have a lot of room from past to present to make it any time period.
The story will probably not be similar, but you're crazy if you think there won't be major easter eggs linking this game to the other two.
If I was to guess, I think this game takes place a few years after the 2nd one, cause I'm not sure, but pretty sure that the girl in the gameplay video is Elizabeth from bioshock 2