1) Legit, in my book, either means a new type of triple A budget open world game, or an HD new version of the handheld games. Pokemon Stadium or any other thing they may call "mainline" wouldn't count, but I get your point and i am inclined to agree that their definition of mainline is the same as ours.
2) Then they will canabolize each other.
1.) At E3, it was specifically announced that Game Freak is developing a "core Pokemon RPG". Game Freak has literally never made a single Pokemon game other than the mainline titles.
2.) X/Y and Sun/Moon are going to sell over 16 million each, Diamond/Pearl and Black/White sold 17.67 million and 15.64 million respectively. If that's your idea of cannibalization, are you predicting that Animal Crossing is going to sell 16 million at minimum on Switch?