That was my guess too,that they will wait to see how it does,to decide later on. That's what they also said they would do for WiiU,before that console was even released.
I think that Valve's platform has a bigger potential to be succesful than Nintendo's though.
Nintendo started WiiU by promoting a controller with a screen as a selling point instead of graphics like other consoles did,and sold consoles with the premise that "some day it will have games",while Valve's system is already going to have 'graphics' and a new controller at the same time. Except from that,from the few things I know it's much easier for someone to work with Valve and have his game on Steam,than work with Nintendo and have his game on a Nintendo system. Getting a license from Valve is much cheaper and easier than Nintendo,and at least for indies it will be a more desired platform to have their games on. I still wonder how big devs and publishers will see that though, the fact that Oculus Rift will not come to ps4 / xbox one / wii u,and that Valve has said that is teaming up with these guys for mutual support is of course another thing to consider for the future of Steam Machines. So if VR goes matched with Steam Machines,Valve can have a selling point there. But there is no clear idea as to how much and which way Oculus will be supported by Valve.I don't know about Steam Machine devkits,but Oculus is pricing their own 300$ (quite cheap if you consider WiiU devkit costs thousands) and the guys at Oculus are already providing plug-ins for popular engines like Unity and Unreal,and they say they will make more,and have made these quite easy to integrate from what I know.
If making a game support VR is as easy as they make it seem to be,and VR is actually as exciting as people who bought the dev kits on Youtube make it seem to be,and the only console like machines that play VR are Steam Machines,there can be a number of people getting Steam Machines just for the VR gaming.Now the reason I compare Steam Machines with WiiU is because they are both systems that aren't 'standard' consoles with the traditional way but are coming to an alternative of what is considered 'standard'. Because it's easy to predict that ps3 and xbox360 owners will make the jump to ps4 and xbox one,but with the Valve and Nintendo the users of their platforms hadn't been exactly the same audience as those who buy SONY and Microsoft consoles. What Valve is trying to do though is have all the boxes checked. A system to be marketed for both graphics and new controllers,targeting both traditional console gamers and pc gamers.It's a unique experiment actually - trying to fuse two different platform philosophies in to a single product,trying to capitalize the best from both worlds.
Of course the future is to be seen,but my honest opinion is that Valve has much more potential than Nintendo to go well in competing in that space.