I reckon no one can say for sure but given what we know about western geopolitical machinations we can safely presume that the Darien Gap remains closed by design rather than by nature. To put a road/railway through there would require no special technological marvels even by standards of 1914 when the canal was opened. People have taken vehicles though there on numerous occasions already. Putting a road through there would be of economic benefit for those people who live there. I don't know for sure put I would suspect that area would be an ancient trading route of indigenous peoples.