Will it course any problems to use a 4.8V battery ?
For the microcontroller you will need at least 6V, as HDL_CinC_Dragon said. You could always use a 9V battery for it. I give that option in the $50 robot tutorial.
For the motors, 4.8V will work. But . . . ignoring all mechanical problems that tracks cause, there are energy efficiency problems. Tracks have very high friction, meaning they are much less efficient than wheels. This means less torque, and a higher drain on batteries.
So . . . a higher voltage battery gives you higher torque. Perhaps important . . . I'd just test out the 4.8V and see how things go before making the investment
Anyway, if you are going to use tracks, you are required to post video of your robot going through rough terrain