Warner has announced Mad Max 2 & 3 on 4K BD in the US too now. See new forum threads that just have been created:
Mad Max 2
Mad Max 3
No Mad Max 1 as individual 4K BD release in the US it seems though (maybe because Kino already has released it in the US?). But a box set containing Mad Max 1-4 on 4K BD will be available though.