TL;DR: Governments and banks would have a field day. They would say, see, they have inflation. They always preached that there would never be more than 21 million bitcoin. Now there are 42 million. This is the perfect wedge to drive into bitcoin and discourage all users.
Limited supply means nothing without usability. Not like we don't have a huge alt market. SegwitCoin does not offer scale or usability, nor sticks to Bitcoins original vision of peer to peer electronic cash. BCC will become bitcoin shortly after August 1st when people realize Bitcoin was made usable again.