What makes you believe that all those who currently avoid Open are suddenly coming in droves if they have no other choice? Imagine the other way around and Open would be closed, no more PvP at all and everyone would have to play in Solo. How many PvPer do you think would stay?
This - people seem to think that solo players will just play in open without even considering that if the reverse was done, PVP'ers would melt the forums with salty rage dug from the Marianna Trench itself!