Mate, I think that is a HUGE overstatement, and a little bit Dad's Army tbh.
The big bash hasn't killed off state cricket, nor the IPL Indian first class, nor any else.
The t20 hasn't killed off county cricket as a whole, more so it's actually boosted it. Same with the one day comps. Kent selling out county grounds for T20 for the first time in a long old time.
As for the hundred itself, I just don't see how it will negatively affect county cricket.
It's been created as a separate entity, and all the proceeds go back to the ECB to be distributed out to the counties, I also don't see how it'll take fans away from the counties.
It's aimed at getting kids into cricket, as a more fun accessible version of the t20 comp, where all the England players they know are playing for one of the sides, along with a few OS guys from the IPL that they might know.
End of the day, the counties had their chance to do some restructuring, but getting 18 old fuddy duddies to agree on something was never gonna happen.