* Political discontent in Saudi not resolved-Yamani
* "Surprises on the horizon" Yamani predicts
* Consultant says Saudi a "time bomb", change inevitable
By Emma Farge
LONDON, April 5 (Reuters) - Oil prices could rocket to $200- $300 a barrel if the world's top crude exporter Saudi Arabia is hit by serious political unrest, former Saudi oil minister Sheikh Zaki Yamani told Reuters on Tuesday.