People, we're discussing what would happen, not the chances of it happening (which are relatively small).
I agree that Ran would be extremely depressed and it would only happen if Shinichi had no possibility of turning back.
Agreed. Ran doesn't seem the type to move on or give up easily, but I doubt the suicide. She'd probably put up a brave face but have loneliness and despair haunting her eyes for eternity. <-- starts ranting
Agreed. While Ran may get over Shinichi, she probably won't marry. Ever. And Kogoro will definitely be upset and would probably kill Shinichi if he got the chance. I think that Shinichi and Ran would avoid each other for some time and rarely make eye contact or talk anymore. Sonoko would likely feel a bit stuck in the middle at first, then choose to go with Ran and ignore Shinichi.