We'll see. I think this season has really picked up and, true to their word, it seems like they've truly found the direction it's going to go. I wouldn't be surprised if a lot of this new stuff they've brought in starts to get connected, maybe during season 5.
With the whole thing about the Oceanic 6, and the fact that there IS a ship there, and Sayid has gotten off, I wouldn't be surprised if S4 culminates with the O6 getting off the island, and then S5 and S6 being a grand finale where some, or all, of them go back and everything comes together.
Then again, maybe not.