There is no end to Candy Crush Saga in the traditional sense. The game is designed to be endless, with new levels being released on a regular basis. So, even if you reach the highest level, you will always have more levels to play.
However, there is a point at which you will reach the current highest level in Candy Crush Saga. When you do, you will be greeted with a celebratory banner that congratulates you on your achievement. You will also be given the option to wait for the next update, which will add more levels to the game.
So, while there is no end to Candy Crush Saga in the traditional sense, there is a point at which you will reach the current highest level. After that, you will need to wait for new levels to be released before you can continue playing.