Personally I think that when FF14 comes out, many people will not know what to do. Stay in the world you know and love or move on to the new!
I personally will love to see what 14 is and will pay, but in the same time not abandon 11. But for many people that can choose 1 and only 1. I think will stay on 11, as starting from zero is never fun. I am hoping SE has thought more on this, as it may be a repeat off EverQuest 1 > 2. Where many people stayed some moved, and some quit all together.
My opinions are mixed, but what is sure is, unless SE offers something to push people to move, many will not. Especially people in 11 with relic's or other things that have taken month's too years or dedication to the game.