There's always the possibility he's trolling, but I don't think that's Grant's style. He genuinely loves Banjo & Kazooie, and the fans, so I feel like if he knew something, he'd simply not talk about it. If I were to guess, I think this means we may not be getting a new game, at least not yet, as I can't imagine a new game being made without Grant at the initial meetings. The soundtrack was so important to the games and its themes, he was the voice of Mumbo and a variety of other characters. However, if they were doing a remaster, or porting the games to Switch, those could happen without his involvement (at least initially, perhaps he'd update the music for a remaster).