OOPS - sorry - didn't notice this was FTC..
Speculation, to be sure, but FRC seems to be in a four year cycle. The last twelve games, including 2015:
- balls, smaller (?) (Rebound Rumble, FIRST Overdrive, FIRST Frenzy)
- strange bedfellows (Ultimate Ascent, Lunacy, Triple Play)
- balls, larger (?) (Aerial Assist, Breakaway, Aim High)
- Placement (Recycle Rush, Logo Motion, Rack 'n' Roll)
I'd stock up on enough rollers and small motors to pick up relatively small balls for prototyping at least. We'll probably also base our summer camp challenge on small balls this year.