This has nothing to do with Pro, considering standard PS4 is also now HDR capable, lack of current support not withstanding.
This seems like a design omission in PSVR development, but a damn regrettable one - continually switching cables is never a decent solution to a problem because it's inconvenient and likely to cause wear and tear damage. It's also a further inconvenience to using VR and that tech doesn't need further issues preventing people wanting to use it, mild though that inconvenience might seem.
The likelihood of a firmware update seems remote (even if it's possible), splitters are probably rife with issues, so it looks like the only reliable way to get around this for those with HDR capable TVs (an increasing number of people and those first-adoptors most likely to splurge on VR I'd wager) is swapping cables, which is not great and will require different solutions for each persons setup. I think I've come to the best solution I can personally find, but it will mean swapping cables in/out of the back of the PS4 every time I want to switch from TV to VR, every damn time, with the associated wear and tear to the HDMI port.
Poor work Sony, even if it might have been difficult to avoid with the timing of PSVR's design.