DLA to PIP for 17 year old?

Long battle to get DLA for son with Aspergers - took 2 years. But it was nice to have it backdated. Anyway, the court order it paid until December 2020. i.e. now.

Since he was 17 two months, I’ve been waiting for them to tell us he has to apply for PIP at any time but, for now, hes still getting DLA.

Should I chase them up or are they likely to send the PIP forms any time soon?

They will be in touch.
Did you know your son may be entitled to income related benefits now he is over 16?
Are you his official DWP Apppointee?