First of all, Nintendo has always been a "casual" games company. Being a "core gamer" company creates systems like XBox, not Game Boy or NES.
If they are commiting any sin, it is not "abandoning the hardcore for the casuals," but "abandoning the casuals for the non-gamers."
Others have said they are "abandoning the people who got them where they are"--but can you blame them? Those people got Nintendo to 3rd place in the home console race! The people who really "got them where they are" are the DS buyers, not the Gamecube buyers (both of us).
But in a year when Nintendo is releasing a main series entry in the Mario, Zelda, Pokemon, Smash Bros. and Metroid franchises, I'd argue they haven't abandoned their Gamecube/GBA base just yet.
Maybe they will next year, but lets wait until they unveil their lineup! This editor somehow determined Nintendo's long-term strategy from an event where no new games were reveiled. He in fact states that nothing new was reveiled, and the fact that he can conclude anything from this suggests he was predisposed to that anything in the first place.
I hope Nintendo doesn't reveil anything new at E3, because I'm convinved eventually one of these yahoos "in the industry" will literally put on a straw hat and take the ol' guitar out to the porch to sing a Nintendone-me-wrong song.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.
