All the trainers on Route 1 in Alola have one Pokemon. We saw that in E3 stream

All the trainers on route 2 and Skull Grunts have one Pokemon. We saw that in NicoNico stream

If by some miracle the trainers in Trainers school have more than one then it'll be first game where before first challenge all trainers (apart from rival have one Pokemon)

Even XY had several trainers haveing 2 or even 3 Pokemon (one guy had all 3 monkeys) before battling Viola

Its crazy