According to Taiwanese website Sogi, Asus confirmed, via one of its official forums, that the entire ZenFone line would be updated to Lollipop starting April 2015. April next year is also when the company plans to bring Android 5.0 to the PadFone S. A couple of months later, in June 2015, Lollipop should be available to owners of the Asus Padfone Infinity 2 (A86). We assume that the PadFone X (which is similar to the PadFone S) and PadFone X mini will also be updated to Lollipop, but there’s no official word on this yet.
The Asus ZenFone series includes the ZenFone 4, ZenFone 5 and ZenFone 6 - all being affordable handsets powered by Intel processors. A new, 5.5-inch version should be announced in January 2015. Until then, Asus may ship up to 8 million ZenFones (since the first quarter of this year, when the series was released).
source: Sogi (translated)