Slowly getting worse, and slowly becoming more locked down. Petitions won't stop this, at best they delay for 6 months until a "bug" prevents the side loading, they "fix it" now and then it regresses.
Is there any plans for Google to phase out unlocking the bootloader on Pixel devices?
Not sure how more locked down is correct. Malware on Android is common and usually targets those who are technically illiterate, all Google is here doing is raising the bar slightly at the cost of a minor inconvenience of a smaller user base who use a feature.