This is nothing new. The new kid on the block foretells the demise of everyone else. Angry Birds is fun and novel in the way that Pong was. Do you see anyone remaking Pong, even on the Virtual Console? No.
Mobile games are a transient fad, just as as casual gaming is. It will return several times, but it's never going to become iconic or even very well remembered. Angry Birds is the Hootie of the gaming biz, and the Blowfish are now telling Radiohead and The Clash that the public won't care about them much longer.
I suggest this guy go country so he can keep his career going. Those people will accept anybody.
The core of gaming is hardcore gaming, which means consoles and, to a lesser extent, PC gaming. If you want a REAL analogy, this is like a guy who does a web series on youtube telling us that Chris Nolan and the people behind The Office (either version, don't care) will soon be out of work.
Just remember his words, 'cos god knows, we won't remember him