I was re watching Live Together Die Alone last night and the scene where Desmond tells the cop that he wants the book Our Mutual Friend to be the last book he ever reads sure seems different after watching the rest of the series. In season 5 Faraday tells Desmond that the he is special and that he is the only one that can help them because for some reason the rules dont apply to him. I wouldnt be surprised if Desmond is the key variable that will help put and end to this up coming war. I have a feeling in season 6 are friend Desmond might get his flashes back and be able to see what will happen if he is not on the island to sacrifice himself. I think that if Desmond were to sacrafice himself his motivation would only be to protect Penny and Charlie. So he goes back to the island with the intention of dying, just like Michael did.....and on his way back he reads Our Mutal Friend.
Darlton has told us that not everyone will make it to the end..and I think sadly Desmond will be one of those characters who dont make it.