When will the update reach everyone?

The rollout status is 30%. The update to 8.09 should be available for you at 100% at the latest.

….“currently we are at 30 % with this rollout and we will increase the % as time goes by. “….

https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/instinct-3/406371/instinct-3-solar-system-software-8-09 

That was 3 days before ...

Last update from 6.29 (iirc) to 7.08, for me, it was several days to a week after the initial 30% announcement. I'd say mine came through around the time they updated to post to say 60%. I'm the same as I am always anxious to get the update upon announcement, but I just try to ignore it until the app(s) pop up with the notification that's it's ready to install.

You will usually get it quicker if you check for updates in Garmin Express

Try searching for an update through the watch. I wasn’t apart of the 30% but a day later I did a “Check For Update” through my watch and I got it. I believe the % is higher than 30% right now. My son’s serial number is in the 6000’s and mines 11,000’s.

So, after my mid morning walk, I sync'd up with Garmin Express (I don't use the phone app), lo and behold, the update for 8.09 was there! This was about 12:45 EDT. The sync uploaded the package to the watch and when I disconnected it prompted to install and restart. Took about 4 minutes as advertised.