This is a page from garmin.com (google cache working link) for this product https://buy.garmin.com/en-US/digital/p/682155 (not working at garmin.com for now).
It’s a very exciting picture of an empty cell in an HTML table (below). But hey, we know that a HRM-PRO heart rate strap is imminent. About time too.
My guess as to its abilities would be a rationalisation of HRM-TRI and HRM-SWIM to just this one product for all types of swimming and for it to come with running dynamics and BLE plus ANT+ compatability. There might also be some improvements to battery life and on-board cached storage. It’s unlikely to work with the Garmin Conenct app for recording (like Polar’s H10) and unlikely to broadcast 2 BLE channels (like Polar H10).
When? August 29th along with the Fenix 6 launch
Price: I’m guessing at $100/£100, perhaps a tad more at RRP