There's no nice way to say this. Your current iPhone will never be a good VR computer.
Apple's smartphones are some of the best selling on the planet, and with good reason. The camera experience is great, the OS is simple, and there are more apps than any one person will even use in ten lifetimes. It's a great experience as a smartphone, easily one of the best out there today. With all of those iPhones out there, each capable of gaming on a level that competes handily with other portable gaming systems, a Gear VR-esque container seems almost like an obvious push.
That's not going to happen, though, especially not with this current iPhone.
While every other smartphone manufacturer focused on making their display contain more pixels, arguing that a better display meant users could do more, Apple focused on making iPhone displays themselves do more on their own. What Apple calls 3D Touch allows for the application of context to a finger press, and by accomplishing this with a combination of hardware and software the company is able to stand above the competing displays with similar features. While 3D Touch is great, the highest resolution display you can use it on is 1920 x 1080. That's not too bad for most tasks on a phone, but it's basically unusable for VR.
Sticking a phone in a VR headset means taking the total resolution of the display, cutting it in half, and basically holding the resulting display it up to a magnifying glass. On displays like the iPhone 6s Plus, with its 401 pixels per inch, nothing looks good. For comparison, Samsung's Galaxy S7 Edge offers 543 pixels per inch, and when you put both phones in something like Google Cardboard the different is significant. When you combine comparably low OS resolution with comparably low pixel density, you get a VR experience that is less than great. That hasn't stopped apps from showing up in the Apple Store to support Google Cardboard, including Google's own YouTube app, but the hardware just isn't ready to make it enjoyable.
Apple isn't usually first to anything, and historically that has been a good thing for Apple.
This may seem like a fairly trivial thing for Apple to fix, but that thought pattern operates under the assumption that Apple thinks this is something that needs fixing. Apple's hardware has always had displays that are lower resolution on paper when compared to the competition, with a focus on color accuracy and what Apple considered the "right" pixel density for the human eye. A dramatic increase in resolution means, among other things, consuming more power with every frame. That means a bigger or more capable battery, which would mean a slightly larger casing for the phone. None of these those compromises are particularly Apple, but that doesn't mean there's nothing coming from Apple for VR.
Apple isn't usually first to anything, and historically that has been a good thing for Apple. The ability to sit back and see what works, focus on design, and release something resembling a complete thought on the first try is a big part of what has made Apple successful over the last 10 years. It would make sense for that to Apple's playbook for VR, especially when you consider just how many times this particular industry has needed to reboot itself. Apple focusing on a comfortable, lightweight wearable would be incredible as well. Maybe it'll be something that has its own display, and only relies on the phone for processing power. There's no knowing for sure just yet. What we do know now is your current iPhone isn't a great driver for VR, and it'll be a little while before Apple gives its fans something that is.