I think this a really good point to discuss. Firstly I think the flash forwards is NOT similar to one of Desmond's visions in that it can be changed, I think it is set in stone as much as the flashBACKs are. Several things could happen next. They could continue the story essentially from the flash forwards point (2007 ish) about the survivors reuniting and going back to the island. They could carry on being on the island for some time before the rescue happens, watching The Others fight with DHARMA/Hanso/Wydmore for control of the island, before being rescued. Personally I doubt they will continue to have a flash forward every episode, I think this was just a taste of what's to come.