There has been a lot of discussion about that already here and here, and the short answer is 'nobody knows for sure'. But it is very unlikely. And, if this function needs the O2 saturation measurement hardware that the Fenix 6 and other watches have, it will not be possible.
FWIW I have used a Forerunner 945 with this function, and it was real neat in the beginning, it correlated well with how I was feeling - so well, that after a while I stopped looking at it. And now on the Fenix 5 Plus I don't miss it.
