I doubt Van Buren will be considered canon. The Enclave moving all of their forces to the Capital Wasteland contradicts Van Buren. I guess a war between the Brotherhood and NCR could have happened, but whether or not Jeremy Maxson (the guy mostly responsible for the war) even existed is up for debate. There's ways around this, but Van Buren as it was in the design documents being canon seems unlikely.
They could have already incorporated Van Buren lore, into New Vegas? I mean they do take place in fairly the same area, so maybe a mention of this and that, from Van Buren will happen?
Also, I don't think there will be much FO3 reference, except maybe some reference to Lyon's group of BOS moving out East? IF it takes place before FO3.
And also, I figure Tactics, NV, and the others that do not end with a number, just like a sub-series. Like with TV shows and such. You have the main storyline, and events in the first series of shows, that began the series in the first place. Then someone comes along, and maybe expands on a certain character(s) life in another series with the same name, just different person/location. So think of it like that- NV is just a FO sub-series, and may mention some things from the main series to have it still be loyal somewhat to the main series, while still doing its own thing.