I think it's likely that Perl 7 will eventually improve performance in a significant way. That would create a compelling reason to upgrade, either for customer experience or cost reasons.
Use Major Version to break compatibility when it is necessary and bring performance advantage as incentive to switch. It is not one or another but both.
Where there are business value in switching, they will.
It's never going to happen. They don't even think of performance as an important value to have [1]. And in current implementation (without redesigning the language) AOT and JIT compilers are too impractical and too costly to implement.
[1] Even though benchmarks-marketing is a known way to attract users.
I'm assuming that sort of thing will continue, but with less backporting to version 5. Jitting just the regex engine without compatibility problems is one potential thing that could happen. PCRE2 is pretty close to that now.
I don't know who you think "they" are but that statement has not been true for a few years now.