tl;dr: Browser vendors are planning Interop 2027, and Mozilla is letting developers upvote CSS features to prioritize. Top candidates include CSS `@function` definitions, `corner-shape`/`border-shape` for squircles and custom borders, Level 2 Anchor Positioning, scroll-triggered animations, `reading-flow` for accessible tab order, `interpolate-size` for animating to `auto`, gap decorations for grid borders, and sticky/scroll-state container queries. Most are already shipping in Chromium and usable today as progressive enhancements.