At the end of Season 4, the island was moved in time and possibly space. The island was moved back to the days before the purge that was led by Ben and Richard. This is referenced when Faraday most likely visits Chang, Halliwax, Candle, etc. and lets him know about the events that are going to happen to them. All people on the island have moved back to this time.
By moving back in time when the Dharma stations are made and new, The Orchid station is still in working order. I think it can be believed that John Locke and Richard Alpert see the change that has happened and their main objective is use the Orchid to either move in time back to present, or uses it to quickly transfer (like the rabbits) off the island to warn Jack. Or, he moves the island again, never being able to go back. Also, if they move back in time that could also mean that the Galaga sub-marine would not have been destroyed yet and they can take it off island. These are the possible ways Locke gets back. Personally I think he will move the island again.
What happens to Locke off island that makes him commit suicide or be murdered. What I think happens is that Locke visits the Oceanic 6 as well as Walt and lets them know that bad things that have happened before him moving the island again, and by them going back will somehow fix the time traveling island. Locke made a sacrifice by leaving the island for the greater good of the island, knowing that Jack is supposed to be the leader now. When Locke gets back, he loses the use of his legs again and commits suicide. Or, Locke leaves the island by sub-marine or Orchid and is found out by Widmore and is murdered. I feel either one is plausible, but I like Locke making a sacrifice.
How the Oceanic 6 is going to get back is going to be through the help of Ben and Richard combined when richard comes off island (whether its by sub-marine or whatever). They together will show them the way to get back and the whole rest of Season 5 will be Jack convincing everyone they need to go back. The reason why you cannot go back to the island after you have moved it is because I personally think every time the island is moved, it goes back in time. Therefore making it dangerous (as in the Orchid video with the two rabbits appearing next to each other and Candle, Halliwax saying it was bad) for Ben to go back and see himself younger. This is also why he tells Widmore you have changed the rules by killing Alex because the island has moved before with young Ben growing up and experiencing Widmore attacking the island. Once the island moves it rewinds and happens all over again. This is also why Ben knows everything about everyone that comes to the island, he has experienced it before and he makes files for everyone, just like Faraday's notebook. That is also why Ben has no fear at all about anything and always "has a plan." Somehow it changed this time, by killing Alex. This is why Ben leaves the island to get revenge on Widmore's daughter. But I do feel the crash of Oceanic 815 was the first time it happened, and this is why everything got all screwed up and the rules changed as Ben put it.
Let me know what you think, these are just some random thoughts basically thrown together so sorry if there is some holes in my theory.
Theory by Dacious
By moving back in time when the Dharma stations are made and new, The Orchid station is still in working order. I think it can be believed that John Locke and Richard Alpert see the change that has happened and their main objective is use the Orchid to either move in time back to present, or uses it to quickly transfer (like the rabbits) off the island to warn Jack. Or, he moves the island again, never being able to go back. Also, if they move back in time that could also mean that the Galaga sub-marine would not have been destroyed yet and they can take it off island. These are the possible ways Locke gets back. Personally I think he will move the island again.
What happens to Locke off island that makes him commit suicide or be murdered. What I think happens is that Locke visits the Oceanic 6 as well as Walt and lets them know that bad things that have happened before him moving the island again, and by them going back will somehow fix the time traveling island. Locke made a sacrifice by leaving the island for the greater good of the island, knowing that Jack is supposed to be the leader now. When Locke gets back, he loses the use of his legs again and commits suicide. Or, Locke leaves the island by sub-marine or Orchid and is found out by Widmore and is murdered. I feel either one is plausible, but I like Locke making a sacrifice.
How the Oceanic 6 is going to get back is going to be through the help of Ben and Richard combined when richard comes off island (whether its by sub-marine or whatever). They together will show them the way to get back and the whole rest of Season 5 will be Jack convincing everyone they need to go back. The reason why you cannot go back to the island after you have moved it is because I personally think every time the island is moved, it goes back in time. Therefore making it dangerous (as in the Orchid video with the two rabbits appearing next to each other and Candle, Halliwax saying it was bad) for Ben to go back and see himself younger. This is also why he tells Widmore you have changed the rules by killing Alex because the island has moved before with young Ben growing up and experiencing Widmore attacking the island. Once the island moves it rewinds and happens all over again. This is also why Ben knows everything about everyone that comes to the island, he has experienced it before and he makes files for everyone, just like Faraday's notebook. That is also why Ben has no fear at all about anything and always "has a plan." Somehow it changed this time, by killing Alex. This is why Ben leaves the island to get revenge on Widmore's daughter. But I do feel the crash of Oceanic 815 was the first time it happened, and this is why everything got all screwed up and the rules changed as Ben put it.
Let me know what you think, these are just some random thoughts basically thrown together so sorry if there is some holes in my theory.
Theory by Dacious