On the other hand, nobody knows for sure when 5 will be released, so why artificially wait?
I don't mind if we wait for 5 or just upgrade to 4. But we should still update Scintilla 3.x in current master and get it released. Afterwards, an upgrade to 4 or 5 is perfectly fine. I just want to get a new release with the current 3.x release for users with old compilers (if there are any at all).