Emily Rogers is a famous blogger who speaks mostly about Nintendo games. She often gets confidential informations and leak them sometimes. I don't really recall a lot of her leaks, so I'll let someone else speak for me about her.
However, I know more about the second guy behind this rumor, Liam Robertson. He works for Unseen 64 (YouTube channel about cancelled games and leaked informations about upcoming games), he got a lot of informations and generally he's pretty careful when he spoke about rumour. I remember him leaked that Devil's Third was let down by Nintendo of America and edited by xSeed, before NoA took it back because of the backlash. He also leaked the Mario vs Donkey Kong amiibo challenge, and some others stuff like that. I think he's reliable, he has made mistakes by the past but he's most of the time pretty careful about his rumors.
(I absolutely don't know who's the third guy)