Status of child when parents switch to ILR

Hi,
My wife and I will be applying for ILR next week via Tier-2 General 5 Year Route. We have a 3 year old child who born in UK while we were on Tier 2 and has a Tier 2 Dependent BRP which is valid until Jan 2021.

We are planning NOT to apply ILR for him as he will be entitled for BC if we can get our ILR.

My question is, is the visa of my child (Tier 2 Dependent) going to be cancelled when we got granted ILR? Can he travel out of UK and come back with his Tier 2 Dependent BRP, before he receives BC and then the British Passport?

Thanks in advance.

is the visa of my child (Tier 2 Dependent) going to be cancelled when we got granted ILR?

No.

Can he travel out of UK and come back with his Tier 2 Dependent BRP, before he receives BC and then the British Passport?

Yes.

Thank you!