LG has confirmed that G4 users in Poland will first receive the update next week with other markets in Europe, Asia and the Americas to follow.
Historically, that could result be a wait as LG has seeded its update to Poland first in the past, only to have the wider rollout around four months later.
The update will probably be released over-the-air. According to recent researches at the University of Cambridge, LG is the top OEM for issuing Android security patches.
LG will announce which other smartphones in its line-up will be receiving Android 6.0 Marshmallow in due course. It will also reveal an upgrade schedule soon.