Google to finally bring 4K@60fps video recording to Pixel phones - Mr and Mrs Tamilan
Interestingly, the teardown is done on a still-unreleased Google Camera 7.4 APK, allegedly obtained from a Pixel 4a smartphone. That one certainly won't have the new video recording mode as its chipset doesn't support it but perhaps it will be seeded to the Pixel 3, 3 XL, 4 and 4 XL, which have the processing power to handle it.
In a less positive development the feature might only come with the upcoming Pixel 5 lineup in the Fall and Google is just preparing for it now.
Source: https://www.gsmarena.com/google_might_bring_4k60fps_video_recording_to_pixel_phones-news-41971.php