Update: Marc has directly confirmed his retirement with us and many others. The future of Half-life will be with someone else. Although unconfirmed, user @TeddyWolf posted an email exchange with Valve writers Marc Laidlaw which states Marc as having retired from Valve and that "My time working on the series [Half-life] is behind me" The email comes from an address known to be Marc's personal gmail and is listed on his personal website. The content in the email come across as very genuine however it is a little strange how Marc has decided to reveal this news. You can read the full email here however we are still awaiting confirmation from Valve whether this is legitimate.