While one switch will work just fine....you might want to consider where these lights are going and what your purpose is for the lighting. Is it to highlight certain things....just provide general lighting....etc.
It may be more work, but depending on your purpose.....you may find it nice in the long run having a separate switch for each set. Plus....with track lights....I'd recommend wiring them to a dimmer switch. If you decide to wire each one to a separate switch....you could still use the same circuit without problem.
Surprising you actually have a run of wire in your house with only one existing light on it! The way they built my house....the wiring is nutty. Works just fine, but I had to figure out what did what when I finished my basement, I almost went bananas.