Which is more likely to happen..?

The dumb person becoming smart. So if the dumb guy is in a room where people are pondering philosophy, he can learn from them, expand his mind and start to expand intellectually, if even marginally. But a smart person cannot contract his mind...at least not as quickly. Even if the dumb person learns one minuscule new fact, he is smarter. Can't unlearn something once you're an intellectual.