You should not expect 8.1 update in July, I wouldn't be surprised if they skip 8.1 like they did with 7.1.2 nougat. If they keep releasing more phones during 2018 then Nokia 3 can kiss Android P goodbye as well.
Yes, I also agree with @Notiz on this one. Nokia is releasing too many phones, I am skeptical about HMD handling so many Android OS upgrades for so many phones on time. And, I won't be surprised if Nokia 3 didn't get get the Android P update.
I have asked Juvo sarvikas on Twitter about major updates for Nokia 2, 3, 5, 6, 7,
& 8 (2017)..., they replied me they will get major updates like android Oreo (O) & android Pistachio (P) alongside with their new variants Like, Nokia 2.1, 3.1, 5.1, 6.1, 7+, and 8 sirrocco, hence we will get Oreo 8.1 alongside with Nokia 3.1