Vivoactive 5?

That new HR sensor is very promising...

I think, there is a new optical HR/PulseOx sensor. This should be nice upgrade, current PulseOx readings are literally HORRIBLE. 

I"m not that sure it's a sensor problem, I think that their software is messy in calculating correct SpO2, I've already reported about this to support and you can try to do that to, maybe they fix it at some point.

Only improvement may be sensor, but it still unknown how much (if any) better it is than the current sensor in Vivo 4

The YouTuber "Chase the summit" compared it to the Fenix 6 and a chest strap and said that it was nearly as good as the chest strap, better than the Fenix 6...

Reviews for new product always say it is much better than previous version, but after some time and some real-life usage it shows that imorovements are not as big as anticipated.

it would be cool to have the only device for tracking heart rate but optical HR sensors so far fail at this, at least those which you wear on the wrist,  you can get way better results wearing them near shoulder from what I know.

They can slightly improve battery life and add sleep widget the way the did on Venu 2 but I've some doubts that Vivoactive 5 will appear at all, because if they would add these features they would become more and more like Fenix and it would be harder to distinguish one from another. I think there are more chances for Fenix with touch screen to be released at some point.

You might be correct, but in this case he had an actual diagram showing the differences. But yeah, we will see. I guess till then I will have a Fenix 6s that has its beta phase already done...