Clearly what you are doing is working so keep doing it!
If he is responding positively to your teaching just keep teaching him. Start teaching him to read and write and spell, teach him to run and a ride a bike, teach him to count, add and subtract, teach him the time, teach him anything he is interested in. Dinosaurs? Worms? World history?
Don't worry about the future just teach him what he wants to know now. School is a lot easier at the top of the class than the bottom!