I still don't trust Nokia that they will provide Android O for Nokia 3.
Many companies have lied about updates before. Nokia 5 and 6 will get it for sure but Nokia 3 is suspect.
Nokia always delivered on their promises.
Problem here being that this is HMD, not actually Nokia. So they still have to prove that they actually kept the spirit they had when they were officially part of Nokia. So far, I don't think so.
For example, I did something I NEVER did before, even less to a Nokia device: I returned the Nokia 3.
The build quality is amazing and the LCD screen, considering it's LCD and in a phone that costs 170€, is great...but that's it. Everything else is just horrendous. The thing lagged and froze out of nowhere, the camera was utter crap...the experience just wasn't good.
And without root, it was impossible to salvage the phone. So back to the store it went.
That alone doesn't make me too optimistic about the future Nokia phones done by HMD if they keep following this path. Even if they deliver updates on time.