There's a lot of misinformation going around about this... simply put, it's going to be a rough road ahead for gaming channels on youtube, but it won't kill them off.
I think it's ironic how there's YouTubers who have spent time and money for years making sets and skits to barely get 1M views. Yet over half of the top 20 paid YouTube partners are people who sit on their butt and play video games while prank calling people or harassing other players. Be done with them.
The Meaning of Life, the Universe, and Everything.
Top 20? Not really (only a couple of the top 20 are "sit on butt and play games"), though the top 100 is a different story (it's close to 1/3 there if memory serves).
The issue youtube seems to not realize, is gaming is the vast majority of the long-tail, and a good chunk of the spike... So I don't think they realize how drastically this is going to impact them (Not sure the cause of the change to MCNs, but it's there - the ContentID system has not changed, it's no more 'anti-gaming' than it was before the change, it just applies to more people)
I could go into more detail about how it all works, but yea - this isn't the place. Simply put, it's not the end of gaming channels or even Let's Plays, but rather an end to the 'way we do it now'. (I'm not an LPer usually anyways)