Kurt's stepbrother defended Kurt (from assault and harassment) at times, so there was a bond between the two, and perhaps to bring some joy to his stepmother, Kurt might want to name his kid after Finn someday.

Obviously, 'Finn' should be kept for Rachel or Kurt in the event that one day they may want to use the name for one of their kids. Hope the writers don't screw up the baby-naming.
Given that Will is friends with Burt (former campaign manager,) he'd have the decency to get permission to use the name (maybe use it…