The June 30 cutoff closes open-source maintenance for the 3.5 line — no more free patches after that date. Spring Boot 4.0.6 is already the current stable release, so the migration path exists; the question is how many teams running 3.5 in production haven't started the work yet. The commercial option (VMware/Broadcom's paid support) extends coverage another 72 months, but that's a procurement decision that takes time. Teams with a hard no-commercial-support policy have roughly four weeks to plan a 4.x upgrade. That's tight if the delta includes framework-level breaking changes, which the 3.x-to-4.x jump typically carries.