He hasn't been right about anything since the game launched.
So it's a NOPE for me.
This is false, though.
He was right about Terry, Erdrick(not everyone knew there was going to be alts, after all). Even if you don't want to count Terry, which makes sense, due to the other leak(though unlike Sabi, he didn't "wait" to release the information. What really happens in these situations is Vergeben has stopped releasing information till he's completely sure of it. He knew of Terry beforehand, sure. But until the SNK leak, he wasn't willing to go 100 into it. He never tells us anything unless he 100% believes in it, period. All the SNK leak did was further confirm his information, but it is not why he knew of it at all). Banjo & Kazooie too, though he didn't say that first(but for his case, he clearly has his own sources. He doesn't piggyback off of people anyway), but there's no reason to credit him for it either way. Nobody knew about Byleth or enough to speak up. He probably did, but after getting destroyed by leakbait in a Nintendo direct, he's in "without a shadow of a doubt mode", which is very very smart.
It's more he hasn't had a perfect track record on DLC. But there's no use in denying the Erdrick bit either. He had the information way before the datamine and told us. He also was clearly not informed about any alt situation, or had no confidence in bringing it up. But he was definitely not wrong. He also never even gave a conclusion about Erdrick other than "he's playable", which is still accurate. If he had said that there's no other alts, then he'd have some false information. But the lack of answers means it is pointless to use that kind of information against him.
To note what's interesting about the Hero thing is many people came to the wrong conclusion that Erdrick was the face. Others didn't think alts existed either. Some thought he was the face with more alts. A very small amount of people(at least that I could from these forums only) predicted Luminary and Erdrick as costumes, and Luminary probably being the face(note, I did predict this myself, but I'm just one guy who got it right at best. And I didn't even have all the alts. I just guessed we might get Eight. Solo I had no clue on either).
Leaks aren't black and white.