Oh, they expanded the player base alright. You can see the results any prime time in the MA. The results are not pretty, particularly on the text buffer. The resulting "HordeWarrior" gameplay style isn't anything to be cherished either.
Adding players did not, does not and would not necessarily "improve" the game.
As to your assumption that without an expanded player base there would not have been an AH2, it's an assumption.
IIRC, HT said AH1 was a success, so it's unlikely it would have just faded out without GV's.
The only thing GV's added was something to do for the guys that don't have enough persistence to learn to fight in the air. They make "fighting" more simple.
Were they removed in toto tomorrow I seriously doubt it would spell then end of AH.