It's only a matter of time how long that relationship can last since the show is done. They either grow old together or break up a month after the last episode ended. Hell, my favorite Korra ship is a polygamy ship where Mako marries both of them while the Korrasami ship is still fresh.
Which is actually the foundation of a strong and healthy relationship.
i really needed this to be canon. i got my wish
Korrasami: NOW CANON