I don't think you let Anderson go until the deadline next year and that's if and only if Lehner has proven to be able to handle the load which I think he will. If Anderson does get traded in the off season it's because they have full confidence in Lehner but as we have all seen having depth in goal pays off... 2 guys you can count on is so important.
I think an older guy for Lehner is the way to go as well and looking at the guys that might be available around that time, Emery sticks out the most to me. (Guy will be 32, 33 which is diff than mid 20's Emery). That said perhaps they want a capable backup that they want to develop like Lehner, Driedger then sticks out. Give the reps to Hogberg and Brassard down in the AHL/ECHL. Anyways, we'll see.