Well a standalone headset is the ultimate goal, of course - or even contact lenses that can seamlessly do AR or VR. But for now, a standalone headset just isn't attainable. The power requirement is quite high (~160w or so to hit steamVR ready, I'd guess, assuming 45w mobile i7 and GTX 1060 with a very lightweight system build using good parts) for any sort of helmet, and the headsets can get pretty hot even without heavy duty processing going on inside. The other major issue is inside out tracking - it can be done, but it adds hardware and processing needs, which all add to the cost. Hololens is the closest thing to a true standalone headset, and it's not capable of nearly the pixel fill or resolution that a Rift can display, and it costs a Heck of a lot more. Heck, hololens Dev kits are pushing $4k on ebay, and I assure you microsoft is selling them at a notable loss (based on their stated 5 year time to market for business customers, I'd guess each headset costs them around $20k to make, not including R&D - puts em around ~$2k each when it's time to put em on the market, which is very fair for enterprise customers.).
So for now, PC-attached is the way to go. I suspect we'll see something that has a tablet class SOC integrated into the headset, with a wireless or maybe tethered external tracking camera/lighthouse/whatever inside of 2017, but it simply won't be competitive with PC-attached options.
As for the development of PC attached sets, I do fully expect to see a headset with a battery and wireless data connection - probably like 60ghz wireless - relatively soon. The cables are the real bane for now, after all, rather than being in proximity to the PC in the strict sense.
It's also worth noting that the power requirements for seriously good VR are gonna be climbing pretty fast for now. Heck, the Nvidia Funhouse demo recommends SLI GTX 1080 for render and at least a 980ti for dedicated physics and audio for high settings. Gen 2 rift and vive will almost for sure be based on the new higher density SAMOLED panels, which will result in probably ~50% more rendering load at the bottom end, and I wouldn't be all that surprised to see the framerate go up. Then sometime around 2020, or maybe sooner, we'll see lightfield displays hitting the market, which will solve lots of lensing and weight issues, but will introduce higher rendering requirements (that's where nvidia is going with the Simultaneous multi-projection in pascal - they wanna be able to render hundreds or thousands of viewports on the same scene for lightfield displays). Ultimately we want to see 16k per eye at >144hz as soon as possible. I'd guess that in 5 years we'll laugh at how primitive the Rift and Vive were compared to what we'll have then, just like how we laugh at DK1 and cardboard today
