The truth is that no one knows exactly what will happen to Bitcoin.The technology is interesting and there's a lot of money and confidence tied to it. It's hard to see another coin replacing it soon BUT it can happen.
Bitcoin hitting all time highs will most probably bring in new speculators and price will skyrocket. Bitcoin prices dropping also brings in the same speculators who think they can buy low and sell on a rise. For this reason, my personal belief is that Bitcoin will always maintain the leading position.