Desmond's possible role in the finale?

[ScienceVsFaith]

Richard said that he watched everybody that Sun knows die in the past. Recall that Desmond is the ONLY one who is different and can change things. Is it possible that the losties will die and Desmond will be able to change the past?

[MagicoA]

Richard said that he watched everybody that Sun knows die in the past. Recall that Desmond is the ONLY one who is different and can change things. Is it possible that the losties will die and Desmond will be able to change the past?
either they change the past with des(finger crossed!) or richard saw an explosion at the swan and assumed them dead but they put the bomb as a fail-safe