"There's no financial incentive for ISPs or any companies to invest in IPv6"
Carriers are running out of public IPv4 addresses. When they do, they'll have to deploy multi-layer NATs (so called Carrier-Grade NAT (CGN) or Large-Scale NAT (LSN)). This presents a problems for the ISP: Cost. Right now, the ISP don't pay for NAT. Their customers do. With CGN/LSN, the ISP now has to run NAT. That's a financial incentive to deploy IPv6 (with IPv6, there is no need for the ISP to run NAT).