Someone correct me if I'm wrong, but didn't smartphones go the "upstarts unseat giants" way? Apple wasn't a phone-maker, and became huge in the phone-market after their launch. Google also wasn't a phone-maker, yet took over the market slowly but surely with their Android purchase.
I barely see any Motorola, Blackberry, Nokia or Sony Ericsson phones anymore, yet those were the giants at one time. Now it's all iOS/Android, two "upstarts" initially.