How bloody, you ask?
Consider that a Sunni victory means the entire world falls under the Caliphate (a codified political system) - this means that of the billion odd Christians, most would be put to death; count the Hindus as another billion dead; all others (from minor religions to atheists) would mean still another billion. So there is three billion dead. Horrible you say. Unthinkable.
Then there is the victory of the Shia Twelver sect - the current ruling mullahs of Iran; three billion for them is just the start. Their goal is to bring ALL of humanity to Paradise. Total extinction. Think on that.
Islam will keep on going until it is utterly destroyed or is totally victorious. The more thoughtful, kind, and tolerant we are now (in the current stage) toward Islam and its adherents, the higher the body count later. The choice is basically the same one Truman had to make - nuke Japan or suffer more tens of thousands of our soldiers dead.
Oh I agree that real Islam insists that it’s either them or us. There is no peaceful coexistence in their book.
I think that the time is rapidly approaching when we take up their challenge and demonstrate that while we didn’t invent war we damn well perfected it.
Islam will join the Aztec religion as one more murderous cult that wore out its welcome and whose extinction was desired by all of its neighbors.