You are quite right and from the look of things it will remain like that till anytime anyone can't imagine. The reason for this is, Bitcoin is totally decentralized unlike most which claims to, and also Bitcoin overtime has grown to be valuable hence having a huge community backup. Also, most people today trust Bitcoin more than other coins and so far this remains the case, hardly will any altcoin overtake Bitcoin. In the same way, in the case of altcoins, most can't even be trusted nor work with their roadmap to develop a platform valuable. Therefore, you are right but things will not change, Bitcoin will always remain on top.