Yes but for now, you can't just assume that they do. I think only law was confirmed to have it. And by feats, they haven't shown anything that can come close to neither zoro or sanji. You're basing your opinion on the mere fact that sanji isn't a captain, but that's just wrong. We've seen it many times, an underdog who isn't even a captain taking out big shots. Just look at rayleigh for example, he was fighting kizaru despite him not being the captain. Having said that, we truly don't know how strong they are, and most likely, the will show their powers sometimes in the next chapters but, you can't really say that they're stronger when they don't even have the feats to support it, it's like me saying that saying that sanji will have haoshuko haki sometime in the future and thus he will be strong enough to beat them. Man even top dogs in cp9(lucci,kaku,Jabra and buleno) can probably take out some of the super nova.
Again, assuming stuff won't get us anywhere honestly,because we can all assume stuff when it comes to potential , and thus, those from the supernova who hadn't shown haki or was told to have it, cannot use haki as forr now.