Whether the stable boy will be back I don’t know.
My reading at the time was that he was ‘representative’ of there being more force sensitive beings throughout the galaxy. Rather like Chirrut in Rogue One. That reading also plays in to what Luke says; “To say the Jedi dies, the Force dies, is vanity”.
Maybe he will be back though and Lucasfilm are sewing seeds for later like Disney have done in the Marvel Universe movies. Who knows.