Why do you presume we won't have nuclear weapons by the '50s? Or for that matter that the Sultanate will have any compunction against dropping chemical weapons on infidels during a Jihad? Come the '30s the Sultanate Air Corps will be truly preposterously large, certainly more than capable of plastering the colonies with enough WMD to do some depopulating of our own.
I'm pretty sure that Steve issued an edict to the effect at the start of the game that nukes wouldn't be available until the mid 40s because of, well, me and Shep. If it wasn't an edict then he did otherwise indicate that he didn't want the game to turn into a "RACE TO THE BOMB" game.
EDIT: Whoops, for some reason I thought you said "bomb in the 30s".
I'll grant you that after a point nukes would make a war inconceivable if only because everyone's so damned close together, but that's a long ways into the future.
EDIT: You know what? I'm so fucking done arguing about this stupid game. I've stated how the Sultanate will handle the situation: one way or another the colonies will have to go. Y'all want to write an epilogue? Then that's what you're going to have to deal with, and if that means the epilogue will be "bombs fall, everyone dies" then so be it. This was a shitty-ass world anyhow.
Wish you had told me before hand that you had cracked Sieges account.