They seem to be going low-moderate risk/investment. Sure there's progress, but then the Wine devs are moving pretty steadily too at the moment.
If Valve wants to really be serious:
- Offer incentives to Devs to support Linux/Vulkan
- Release a goddamn new game (HL3 - dreams) and make it Linux exclusive for a time
- develop and release new features for Linux first (maybe if GoG ever get the Galaxy client over to Linux Valve will get a kick in the pants to act...)
- Promote SteamOS and (maybe) Steam Machines, like at least some. Show Steam Machines as an 'out-of-the-box Windows gaming replacement, not a console competitor.
- Fund Linux devs or take a lower cut from Linux releases
- Convince Adobe to release their suite on Linux! Push for/fund official Unity and Unreal Engine Linux versions
- Offer the ability to natively launch games through Wine (and either use 'community' environment files or require one exist, or have a link to WineHQ for help)
Be serious Valve, be genuine and get your flat structured 'follow the shiny thing' company focused and determined.