I live where they salt the roads in winter. I normally have to dismantle the brake calipers & clean them up, at least once during the lifespan of the brake pads. They don't need new rotors, just clean up the rust & dust.

Of course, I'm not looking directly at YOUR brake calipers, so it's possible that the mechanic is right. If I gave that to a shop & pay labor, then I might be inclined to put new rotors on, just because I'm already spending the money to dismantle them.

"... Also would need to replace wheel bearing for knuckle."
So what about the wheelbearing is actually bad? Replacing the balljoint shouldn't automatically require the wheelbearing.