Pentatonics will get you started -- and get you playing pretty decently. How far will they take you?
Well, Jimmy Page and Eric Clapton have gone pretty far with pentatonics, so don't assume this is baby stuff. It's simple, but you can ride the pentatonic pony quite a ways.
However, if you'd like to try other things, then here are some suggestions:
Pentatonics are a start -- but there are other scales! Look into Mixolydian and Phrygian scales. To mix things up, throw in a little of these -- you can always fall back on the standard pentatonics if you need to. You can even do some nice things with a simple Dorian scale (Do-re-mi scale)
If you're fiddling, then you'll want to advance to double stops. Double stops add a whole new level to fiddle improvisation.
Finally, pay attention to styles. The way you do things can be more important than what you're doing -- BB King can hit and hold a single note and tear down a crowd. Listen and try to determine what makes things special. Listen for the "soul" in the performance. The great players have it.