The family that I worked for as a nanny had 7 kids. 6 out of 7 of their kids had teeth pulled and braces on by age 8. Their dad has huge teeth in a small mouth. Because his parents didn't take him to the orthodontist young enough he has a horse tooth look.
If your dentist advises you to do a consult now it's not because it's going to make "him" any money. He has NO vested interest in you doing this. He means you need to take him for a consultation.
They have all sorts of devices out there they need to have installed/put in by age 8. BEFORE their bones are totally adult size, which happens in the next 4 years for most kiddo's. Their hands, feet, ears, nose, jaws, cheeks, etc...are all, at 7 and 8 going to have slow steady growth for a few months then a sudden growth spurt and they'll look odd for a year or two until their skull and shoulders catch up in size.
He needs his devices on now so his jaw bones can be made the shape and size he needs.
I've seen kids wear Bi-oh-nate-ers...don't have any idea how to spell it but that's how it sounds, at age 7. It looks like a mini shock absorber connected to a tooth on the jaw they want to grow and it connects to a tooth on the bottom on the other one. It stretches the parts apart instead of moving the ends together. So if they want to top jaw to expand they'd connect it to a top tooth behind the eye teeth then connect the bottom to the back jaw teeth. Putting pressure on the top teeth constantly to grow and expand.
Another little friend that is not 8 yet had a device in the roof of her mouth that mom turns a click every morning and every evening. Her top jaw is too narrow so this device is expanding her bones a tiny tiny bit each moment. There is constant pressure to make the move as they grow.
If you think about how the Chinese woman of old wore those tiny little shoes you can start to get a visual picture of how bones can be shaped while they are growing. Those parents put shoes of a certain size and shape on their girls at a super young age so they'd have tiny dainty feet. They could barely walk or stand but they had tiny deformed feet.
By starting the shaping process young the process was less painful and easier to do. The same with the orthodontist work, the younger they start the easier and less painful it will be to kiddo.
Make an appointment as soon as you can get in. Listen to what the doc suggests. They have no other goal except to make your child's mouth a thing of beauty.
They'll make money whether or not you use their services so you can trust their judgement.
IF IF IF you don't agree to their observations then by all means get a second opinion and even a third. It's your child that will pay the consequences if you don't start soon enough.