I remember sleeping in places that were infested with rats and waking up with one trundling over my face. Actually, I hate rats! In my time, I've picked up all sorts of things in hotels-fleas, lice, tapeworm.
I think there will be radical changes. But I don't actually think that within the next 100 years the natural world will be reduced to rats and cockroaches, nor do I think that the plant world will be reduced to some kind of desert.