Here's my take on this:
When I decided to switch brands, I waited a *bit* too long to sell my near-mint D700. When the D800 was formally announced, D700 prices tanked by several hundred $ immediately, then recovered slightly after a couple of months. However, the 5DIII was not yet released, and I ended up buying one from the first shipment to arrive in Australia. So I was without a FF camera for a bit less time, but I lost out big on selling the D700, and paid a premium on getting in early on the 5DIII. Thankfully (for me) local prices for the Mark III have remained much more stable than in the US, so I don't feel too bad, especially as my copy has proven faultless (and I didn't have too much invested in Nikkor lenses).
If you sell late due to waiting to see how the replacement body tests out, you will take a hit on your 60D, and unless you are willing to wait for prices of the new camera to stabilize, you'll take another one as an "early adopter". If you sell early, you might do a bit better with the 60D, but with no guarantee that the 70D will give you what you want i.e. dramatically improved high-ISO performance, meaning you might find yourself stepping up to the 7DII and paying quite a bit more.
Until the "truthiness" about the 7DII comes out (i.e. will Canon move to a completely new fab process for its next-gen sensors?) there's no really easy way out of the high-ISO dilemma unless you decide to jump in with both feet and go FF, in which case you're pretty much sure to get the results. If you don't need the burst rate or advanced AF system, I would be taking a hard look at the 6D - 4-1/2 fps is still pretty quick and only a bit slower than the 60D (though buffer clearing is much faster). Download the high-ISO RAW files from Imaging Resource, process them yourself in DPP and see what you think.