That's not how I read it. There's no particular difference between the two roads, so far as Frost can tell at the point of divergence, but they're still different roads and lead by different routes to different places, and he expects that years from now he'll look back and see (or guess?) that it did indeed make a big difference which one he took.
He expects that years from now he'll look back and claim it made a big difference. He says he will also claim it was the road less traveled by, for all that the passing there had worn them the same and so forth. It may well make a big difference, but of what nature no-one knows.
Happy New Year! Here's the latest and greatest installment of rationality quotes. Remember: