I for one am not convinced that the Hydra faction we saw in Ant-Man answers to Grant Ward. The Hydra faction from Ant-Man was led by Mitchel Carson, who was described as the "former head of defense at SHIELD" in 1989. So we're talking about someone who is apparently very high up at SHIELD, presumably just below the level of Director. He appeared to be roughly co-equal in rank to Peggy Carter and Howard Stark in '89, and I just don't find it plausible that somebody that high up in SHIELD or government would answer to a mid-level Hydra field agent like Ward.
On top of that, I just find it really hard to believe that a cabal that had become as powerful and well-ensconced as Hydra -- infiltrating SHIELD from top to bottom, having their leader in the United States Cabinet (Alexander Pierce), putting another of their followers in the U.S. Senate (Senator Sterns), having followers in what I took to be the British House of Lords (the Baroness), controlling large corporations such as Echidna Capital Management (Dr. List), controlling what I took to be important Wall Street banks ("the Banker") and important Middle East-based oil firms ("the Sheikh")... Hydra just seems too large and powerful for me to buy that it's been reduced to a couple of Hell's Angels wannabes in a bar.
So sign me up as one of the folks who thinks Ward has taken over one faction of Hydra, and that the faction we saw in Ant-Man is probably wealthier and more powerful (and covertly controls some large corporation or other upper-class organization), and that the two factions may not be in contact with one-another.