I think they rose a lot of new questions. Especially about the island itself.
***Spolier ALERT***(and sorry, but for some reason, the Spoiler blackout option won't let me use it)
What's up with Sun's relationship to Whitmore?
Where's Sayid taking Hurley?
Are we sure that no one survived the boat? (Faraday?)
What's the future hold for Desmond...and Penny?
And if Desmond is Faraday's "constant"...what does that mean now?
How does Locke get to the mainland?
How does Ben know how to get back to the island?
What's going to happen to the survivors on the island (Others and the last of the "Beach" Castaways that stayed)?
And will we ever find out about the origin of the missing giant statue that only had a foot remaining on it (on the coast of the island)?
Sun's relationship to Widmore is the island. They are both trying to get back for their own reasons.
Sayid is working with Ben, so we can assume that he broke Hurley out of the institution because of what he told Jack - they all have to go back to the island together.
Faraday wasn't on the boat, from what I remember. He was taking the raft TO the boat. I don't think he had gotten there yet, had he? The bigger question to me is whether or not Jin survived. The boat explosion was vague. It blew up from the middle, and Jin was on the end of the runway where the helicopter took off from. It's not entirely impossible that he survived and will be picked up by Faraday and the raft.
Ben always knows how to get back to the island. What will be interesting to see is if he himself can actually go back. He said that he couldn't, and the last scene of him on the island - when he was turning the wheel - was fairly emotional.
I'm sure that eventually, we'll find out the origin of that statue. We can assume, since there was nothing there, that it moved with the island. It doesn't seem like that's something that they'd just forget about. The writers seem fairly meticulous about making sure that every detail is covered, and everything that happens does so for a reason. I'm sure that sooner or later we'll find out.
I was so happy that Desmond and Penny had their reunion. That was a pretty heavy scene. Your question is valid though - what happens to them for the last 2 seasons? We already know that Ben is looking for Penny, and that he wants to kill her to get retribution for Widmore killing Alex. My guess has always been that Desmond will save her life, and that's how he'll become 'worthy' in Widmore's eyes.