Opening on the same day would have roughly zero impact in either park's bottom line. Few attendees are making plans solely on what the opening day of a new ride is, and even the ones that are won't change their medium and longer term plans based on such an event.I don't think they BGW opening Pantheon on the same day that KD opens would be anything more than a well-timed marketing event, certainly not a death blow.
If anything, that'd probably encourage KD marketing to ramp up their efforts - assuming that happens, there's still a net positive.