Singed's entire kit is so unique and has worked so well together as a package, it has become an icon of sort already. In fact, it doesn't seem like Riot has that many extra plans for him, given he is placed in the "Specialist" champion class, which is basically the place where champs go when Riot doesn't attempt to put the champs into the general champ class design and balance scheme because they're too eccentric and unique to be put into them.
At most he would probably only receive some minor reworks to shift things around (like what happened to Nidalee, another Specialist champion), otherwise I wouldn't expect too much changes that would go into him in the future tbh.