On another forum, I was addressing the question whether Desmond mowed Locke down to force a meeting, and "reality awareness," between Jack and Locke. Whether or not that was Desmond's intent, many agree that such a meeting will happen. I think Jack is not only going to save Locke's life, but will help him to walk again (as foreshadowed earlier in the season).
And maybe we will see Locke walk for the first time after Jack fixes him, as a bleed in the MTL: not in 2007, but in 2004 after the MTL loops back to the crash of flight 815.
Remember the time loop that seemed to be indicated by the opening scene of the pilot? Jack awakening in the jungle, running to the quiet beach, the camera angle changing to Jack from another vantage point and suddenly there are crash chaos sounds and images.
With Desmond synchronized in both realities, he is forcing awareness in the ALT that could translate into useful knowledge during the next iteration of the loop.
Maybe the awareness will be complete. Locke awakens after the crash, realizes he can walk, that it is not a miracle of the island, but an act of science performed by Jack. Jack realizes everything Locke had said the 1st time (that we had seen it), about not allowing the freighter people on the island was true and that he should have had faith.
Maybe it won't be full memories, just vague awareness like Locke used to have of upcoming rains, and the way t was "supposed to be." Maybe lots of individual decisions will contribute, or lots of opportunities for different decisions would arise. Desmond may know Charlie should die before inputting the code. Charlie might remember it's not Penny's boat. Locke may continue inputting the numbers because Jack isn't giving him such crap about it.
Whatever it is, in the finale they could just give us a glimpse of the Losties' realization that they have lived this before, and we will be left to hope that they will not repeat the series of steps that lead to the creation of the loop (swan explosion/jughead explosion?) and/or death of Jacob.
I can't think through all the implications and welcome all comments and efforts to set me straight. Thanks.