At the end of season 5, a hydrogen bomb was set off to erase the past events leading up to that point. This means that everyone who had died on the island would be alive again. That means Karl and Alex would never have died and would still be together! Blake Bashoff, the actor that plays Karl, is due to end his run with the Spring Awakening National Touring Cast on August 16, 2009. That means he will be able to do other projects such as coming back to Lost.