Switching brands is rarely worth it. In your situation, you have close to $3000 invested in gear that will only fit on a Canon body. Now you will have to sell that used for what will undoubtedly be a 15-20% loss, and then rebuy a similar setup for a Nikon camera. Your 60D will probably be worth significantly less than you paid for it, too. Your total cost for upgrading might be $1000 with transaction fees and depreciation. And what will you gain? 1fps burst? A few more AF points? A magnesium back?
I think the D7000 is a little better than the 60D, and even might hang with a 7D in some circumstances. But it won't change your pictures really at all vs the 60D.