Well, if they were a brand new start up, I guess they could get away with "end is soon" for a while, but wouldn't that become a new false prophecy after too much time went by for the "soon" to hold water? Even without setting the yearly dates?
There are so many really divisive doctrines here: Blood, War, Flag Salute, Arianism & effective Polytheism, the stubborn Jehovah name fetish, anti-educational rhetoric, anti-government rhetoric, and of course the constant control freaking....
My theory is that this is a little cess-pool of a religion for people who already feel rejected by normal religion & society. In fact, they like the pain and perceived persecutions. Is it possible that the hint of a few past false prophecies and scandals just add to the "isolation and rejection of the world" fantasy for these new recruits? A lot of witnesses don't really acknowledge the existence of any of the failed dates.
I would just guess that their rate of growth would be affected only a very little by removing the false prophecy. There is still so much more there to put off people who expect a normal human experience within a religion. If you are not already born in it, dragged into it by parents, or have a huge chip on your shoulder toward regular society, you are probably not a good JW candidate. False prophecy or not.
Just an opinion, James