Let's be honest, few people care about 5ks or 10ks unless it is during the Olympics or atleast the World Champs.
If you can run a 27:00 10k you definietly have the potential to win every big city marathon, even 27:30s guys like Nelson or Curtis could perform extremely well.
It's true, and they'll be there someday. Even Solinsky said he has the 2020 Olympic marathon in his head (but I wouldn't be surprised if he moved up sooner). They will try to break track records while they're still young but eventually they will move up to where the money and excitement is at