I happen to like the NEX-6 a lot. In fact, it's one of the best cameras I have used. No complains about its image quality, nor its usability; if it were a full frame sensor inside the NEX-6, I would be all set for a little while. But, there is always that little thing called money. Upgrading is usually expensive. For mortals like us who has limited funds to spend on camera upgrades, a $1700 camera is a significant chunk of disposable income to blow on a camera. So what are the options?
Get a Metabones Speedbooster -- This almost gives you the illusion of a full frame camera, but of course it isn't. I am always leery of optics that gets in the way between a lens and the camera. As good as the Speedbooster is, there are limitations; and it does optically modify the lens in front of it. What you get in image is not really exactly the same as what you would get natively on a full frame. And, there is the problem of mounts. If you are like me, who have lenses in many mounts, you would need Speedbooster in different mounts. True, one can get the Canon version and then buy cheap Canon to whatever adapters, but that again, increases the margin of error with double adapters.
I could sell some of my existing lenses to fund the purchase. This is really something I try to avoid. I don't plan to add many more lenses to my collection, but at the same time, I don't want to reduce what I have either. However, if the upgrade urge is uncontrollable, this might be the way to go.
Another option is to sell/trade in my 5D Mark II, and sell fewer lenses. This sounds better to me.
Finally, do nothing. Keep and make use of the 5D Mark II and ignore the A7/A7r ever existed.
Yeah, I know you lucky people are laughing at my dilemma.
Men At Work - NEX-6 & 16-50mm f3.5-5.6 OSS @50mm f5.6 [wide open]. Click for larger.