I think it is likely. Dath has played and beaten Nairo in dittos, and I beat Dath in dittos. Dath also tells me that I would most likely win the ditto vs. Nairo. So it seems a reasonable claim to make.
You're forgetting Dath.
The list of Robin players who currently matter is: Raziek, Dath, Nairo, Matsushi.
Mr. Johan
would be on that list if he had a placing outside of his region (or at a large regional) to give me a frame of reference. Mr. II (Japan) might be on that list as well, but I don't know what kind of results he actually gets. I just appropriate and utilize the tech he posts.
Two things:
1) You're severely underrating Nairo's Robin. I think Dath and I are better (at Robin), but he would still slap the **** out of literally everyone else who posts in this chat just by virtue of his amazing skill as a player.
2) Assumptions that I'm going to 'drop' Robin are pretty baseless. Both Dath and I have expressed our intent to play Corrin. Both of us have said we want to dual main both characters. It's highly unlikely that Corrin would cause me to drop Robin completely unless Corrin is just bat**** busted and totally obsoletes Robin as a character.
I fully intend to play both characters, using them for matchup/playstyle swaps as needed.