Let's remember that Skywalker is a family name and doesn't necessarily equate solely to Luke. Kylo Ren is a Skywalker by default since he's of the bloodline thanks to his mother, so if they go the redemption rout for him, he could change his name from Ben Solo to Kylo Ren to just Skywalker.
Alternatively, if Rey is the Skywalker, then it opens up avenues for exploring the further Skywalker lineage. Did Shmi have siblings? If so, then descendants of Anakin's cousin's could have made their way to Jakku, been nobodies, but have given birth to Rey. Everyone wins, nobody parents, but still part of the overall lineage of the Skywalker name.
Another theory is that since Rey seems to be heading up her own Jedi Order, she might ditch that name and light side Force users become Skywalkers as a title to pay homage to Luke.