It's totally possible. The 100-mile part is only a portion of the overall equation, though. Equally important is how much climbing the route will have. A hilly century is a whole different deal than a flat one, though in my experience anything "non-Fondo" that's 100 miles is generally low on climbing.

I've never ridden 100 miles at a clip before a century. Completing a century is all about endurance and there are lots of ways to build that other than riding 100 miles before the event. Go out hard regularly, do a few long rides, do intervals, etc.