Ok, so there's a lot of speculation going on about the end of this game today. I would like to put my two cents in concerning the finale.
First, from an earlier stage, we learned that The Maxwell Group is a subsidiary of Widmore Industries.
Second, we know that whatever ship Naomi came from is not Penny's boat.
Also, Naomi was in possession of the picture of Desmond and Penny.
Using these pieces of evidence, I am capable of coming to only one conclusion. Charles Widmore, the only other person in the world other than Penny or Desmond capable of possessing that photo, staged the fake plane in the bottom of the ocean for the purpose of ending Sam Thomas' and any other concerned party's search for Oceanic 815. I do not yet know why he is interested in the island, that remains to be seen. These are the conclusions which I have drawn:
There is no wormhole.
There is no time warp.
There is only one Oceanic 815. This is all just a result of a conspiracy. That seems plainly evident to me, thanks to the knowledge that Sam was practically forced to go to those coordinates by The Maxwell Group.
Note: Please do not discuss spoilers in the comments section. I made sure this theory was completely spoiler-free and only used information from the game and show thus far.