Goku will have the most figures made of him, he's the main character. But I'd say Vegeta would be next in amount of figures, then Gohan. Remember Trunks is only around During the Android and Cell Sagas, so once they do 2 or 3 more figures of him and a movie version or 2 he'd (most likely) be done (besides SDCC repaints). Also, unless they start with battle damaged figures, there's probably not going to be another Piccolo in the line, he only has the 2 different versions, which they've already given us. I feel like Tien and Yamcha should be released with just a couple of option parts and make them $10-15ish (I guess, unless it should be more) cheaper than normal, then make a limited test run of an option part set for Tien and Yamcha, and if it does good produce more of it.
Also, if the next figure in the line after Android 17 is Kid Buu I will be expecting SSJ3 rerelease or repaint, Majin Vegeta with normal SSJ faces and base hair & faces, and Mystic Gohan.