The 4 main Clancy universes are in fact linked. They are the Ghost Recon, Splinter Cell, Rainbow Six and H.A.W.X. Right now we currently have the "Before and After", the before being the current games and the after being EndWar, but not the middle.
This is the subject of much debate inside the Clancy fanbases, and the reason many suspect the new Rainbow Six game is taking so long to come out, and why Convictions got delayed so much. Both of these series tended to be "world-movers" in the Clancyverse, and moving too fast too quickyl would totally throw off what they are trying to do with EndWar 1&2.
This is the subject of much debate inside the Clancy fanbases, and the reason many suspect the new Rainbow Six game is taking so long to come out, and why Convictions got delayed so much. Both of these series tended to be "world-movers" in the Clancyverse, and moving too fast too quickyl would totally throw off what they are trying to do with EndWar 1&2.