Lots of progress on AI, alignment, and governance. This sets up a position where it is likely that a few years later there's an AI capabilities explosion and among other things:
 

• Mean human wealth skyrockets, while AI+robots make cultured meat and substitutes, as well as high welfare systems (and reengineering biology) cheap relative to consumers' wealth; human use of superintelligent AI advisors leads to global bans on farming with miserable animals and/or all farming
• Perfect neuroscientific and psychological knowledge of humans and animals, combined with superintelligent advisors, lead to concern for wild animals; robots with biological like abilities and greater numbers and capacities can safely adjust wild animal ecologies to ensure high welfare at negligible material cost to humanity, and this is done

If it was 2028 it would be more like 'the above has already happened' rather than conditions being well set up for it.

The UK government/court bans/decides to phase out fast-growing broiler chickens. https://thehumaneleague.org.uk/article/were-heading-back-to-court

(Not sure if 1 year is enough; I don’t know how long these things take.)

Boring answer: big/many corporate cage-free and broiler chicken welfare commitments.

McDonalds? Maybe McDonalds is >95%, though?

Something with more vegan/vegetarian meals in public school and major college campus cafeterias.

1. lab-grown meat widely available at supermarkets in the US and the EU
2. major action on prop 12 enforcement (https://sentientmedia.org/supreme-court-upholds-prop-12/) e.g. serious legal penalties for the worst offenders
3. serious revision of major dietary guidelines to discourage meat consumption
4. ESG commitments from multinationals e.g. Nestle to substantially cut back on use of meat and animal products