im wondering if i should upgrade my gpu (msi gtx 660 non ti) to a 770 in order to get more fps in bf4 or should i wait for the 800 series
Im not sure about the whole 770 thing since people say its not as good as a 670
While not being a performance beast, a GTX-660 isn't bad at all. It also depends at what resolution and settings you're playing.
Personally, before upgrading something I wait until I get very poor performance in a game. The more you wait, the more performance for your bucks you'll get. So my advise would be to wait until one of your games become unplayable or you start to get very low FPS, etc... I don't like the idea of upgrading "just in case".
You may not feel huge difference upgrading to 770 and definitely not price worth upgrade. I think you may wait little bit longer for the Radeon HD 9000 series volcanic island, which releases sooner than GeForce 800 series.
A GTX 770 will have higher FPS than a GTX 660 to the tune of 20%, but that $400 you're spending will go a lot further in the Maxwell generation set to release in January 2014. Here's a chart that shows relative performance between Kepler (600 series & 770) and Maxwell is set to get a 3x boost in compute power per watt.