Very unlikely. Most likely NAT would have happened to other layers of the stack (HTTP, for example), causing even more problems. Or, the growth of the Internet would have stalled dramatically, as ISPs would have either increased prices dramatically to account for investments in new and expensive IPv6 hardware, or simply stopped acceptong new subscribers.
Your first scenario is plausible, the second I'm not sure about. Due to the growth rate central routers had a very fast replacement cycle anyway, and edge devices mostly operated at layer 2, so didn't much care about IP. (Maybe the was done device in the middle that would have had a shorter lifespan?). I worked at a major router semiconductor vendor, and I can tell you that all the products supported IPv6 at a hardware level for many, many years before significant deployment and did not use it as a price differentiator. (Sure, they were probably buggy for longer than necessary, but that would have been shaken out earlier if the use was earlier). So I don't think the cost of routers was the issue.
The problem with ipv6 in my understanding was that the transitional functions (nat-pt etc) were half baked and a new set had to be developed. It is possible that disruption would have occurred if that had to be done against an earlier address exhaustion date.
