Rumor is that filing such a suit ahead of the election was a GOP demand (as cover for down-ballot Republicans with their own supporters) to avoid trying to have Robinson removed from the ticket. I think it is widely expected to be, ahem, aborted as you note, but the filing law firm has to pay heed to their ethical obligations. I doubt anyone will bring (or would succeed) with an ethics complaint after the case is dropped because presumably it will be dropped at the direction of the client, but no law firm wants to be embroiled in that.