Flashes before your eyes, revisited
Desmond is the key.
Think back to when Desmond is in the ring shop.
Hawking to Desmond, ‘If you don’t go back, we all die.’ What if by “we” she meant the others (maybe even Penny and Faraday).
She even tells him when they are at the Lamp Post station that, ‘the island isn’t done with you.’
Now I know he appears to be wearing a wedding ring in LA X, but what if that ring is kind of like the compass that goes from Locke to Alpert, it’s like a way for him to remember what is at stake and a symbol for someone to recognize him (the real him as it were).
You need to explain yourself a bit further. What does the wedding ring have to do with him returning. Also, I suppose either Desmond could return to the island. As there seems to be a Desmond in each of the two time lines.