They will most likely stay the same as most people will start working on the new Northrend factions and will forget the now "Old World" of Outland factions.
How many people do you see now running Molten Core trying to get Fiery Cores and Lava Cores for Thorium Brotherhood faction reputation?
People no longer care about the current old world factions as the new outland factions give much better stuff. It's now a waste of time to grind old world factions like the Thorium Brotherhood for months because in no time you will be in Outland getting much better stuff.
The same will be true with the next expansion. People will forget about the Outland factions and work on the Northrend factions. New characters, like everyone and his brother who makes a death knight, will just skip past the Outland factions as they level to 80 and grind Northrend factions when they get to 80.
So the Outland dailies will stay the same but just be forgotten by players.