The question really is where do you think the game of AH will be in 2 years?
Judging by the very slow development cycle since the announcement of AHII - over 2 years ago, and the still non-existant "TOD" arena that is still a long way off, I would guess that AH will still be in version 2.x.
At the very least, this means we will be looking at heavily dated graphics and perhaps still listening to only mediocre sounds.
Hopefully, we would have some better gameplay features to keep things interesting, above the level of which country to fly for so you can fly the aircraft you want.
If the above statement is correct, how many new subscribers would there be? As a reference, ask yourself, Would you subscribe to AHII today, if it used the same graphics that were in AWIII or WBII?