Watch the Where to next? online guitar lesson by Rich Maloof from Guitar 201: Breakthroughs
What's coming next in lead lines and improvising is recognizing what scales, or sets of notes, these chord tones and melodies come from. Basically, you're going to expand the available palette of notes and colors you can use, and then begin incorporating those notes into your available vocabulary. Sometimes a single scale will work for holding several chords in a progression together; other times, you may want to (or need to) change the set of notes you're using to bring out the changes and add personality to your playing.