Good! That should be sufficient to address the concern, if you can enable the enhanced CPU. I expect the market for the C65 is big enough to make it worthwhile to hack some enhanced functionality into existing titles, and fix incompatibilities, especially considering that most buyers will have coding skills. Developing native titles is a completely different story... might still happen, but only if the existing people who still develop for C64 get enthusiastic.
I don't know if the C64 roms could switch the cpu mode themselves? You would have to modify them, but it would be more elegant than magic hardware behaviour to auto-switch cpu mode.
By the way, in you Blog post of 19 April you mention you want push the CPU even further to 192MHz, but the website mentions 48 MHz as target CPU speed. Is 192MHz still on the roadmap? centre