1. How much do you think the new ASUS Gryphon motherboard will cost and what do you think the i7-4770k Will cost at launch?
Given it's an ROG board, I'm guessing at least $250. Not really worthwhile unless you love tweaking everything about your computer. And if Intel's track record remains consistent, the next i7 will probably cost $320... Which again, won't probably worthwhile compared to the i5 for gaming (which I'm going to assume off the bat this is what you want to build for)
2. When do you think the GTX 760 Ti will be released and how much do you think it will cost?
Anywhere from 3-6 months after the GTX 780 and anywhere from $250 to $300.
3. Can I use a Radeon 7950 for my main graphics and still use my old GTX 560 Ti for Phys-X only? How would that work if so?
Without hacking the drivers, no. If you want to know how to do that, use Google.