This is the most plausible take on WWDC I've seen: https://www.bloomberg.com./news/articles/2024-06-07/apple-wwdc-2024-what-to-expect-ai-ipados-18-macos-15-siri-updates-more?srnd=technology-vp
TL;DR opt-in enhancements that we've seen from elsewhere like sumisation, better siri, suggestions, an “R2D2” (co-pilot in xcode)