I believe you should probably repot; however if your time is like mine lately, it would probably stay in that pot for awhile longer. hahah... The roots seem healthy, but their color concerns me a bit. With it being that root bound, you will need to be sure to check the center of the root ball. I would guess the grower's sphag plug is still there. That plug should be removed as it will rot the roots around it. I wouldn't increase the pot size by much, but would go up one size as to not over pot this oncidium orchid. Look like a really healthy plant though.

cheers,
BD