IIRC, Lucas is on record saying Yoda came about because someone had to train Luke.
I would think Obi Wan would have resumed training Luke and stay close to the Rebellion wherever they went. Leia and other surviving Rebel leaders would probably want General Kenobi’s counsel from time to time. Although had Obi Wan survived into ESB, he could have sacrificed himself in some way early on, (facing off with Vader again to buy the Rebels time to escape Hoth) and still have directed Luke to Dagobah.
Sir Alec was already dealing with fanboys at this point, and probably wouldn’t have minded being killed off in the second film.
Kind of surprised the Infinities comics didn’t toy with the Obi Wan lives scenario.