In message , at 16:39:51 on
Wed, 25 Jun 2014, Paul Corfield remarked:

I wonder if we will see Southern also extending the Key at the same
time?

They keep saying they will, but without having followed it chapter and
verse, I'm pretty sure it's "delayed".

eg: "To complement the ITSO deployment, Cubic has also implemented new
gate lines at Gatwick Airport and Brighton, the biggest stations served
by Southern outside of London. The next stage of the project will see
Cubic deploy the technology to provide ITSO capability on the remaining
Oyster overground gate estate, with the final stage enabling London
Underground and buses to accept ITSO cards in early 2014."

Is it still "early 2014" ??

People have been anticipating "ITSO on Prestige" since at least 2009.
Including a GoVia press release:

"Introduction of an ITSO-certified Smartcard ticketing system across the
network by January 2012"
--
Roland Perry