Are you sure that the Marshal of the Realm claimed at the 2019 press conference that "Among other things he'd [Prince Carl Philip] be needed as regent if something happened to her [Princess Estelle's] parents and grandparents"? (I do not have a transcript.) That would be a strange and inappropriate remark to make, since the Constitution's Instrument of Government makes clear that it would be the Riksdag (Parliament), not the royal family, who would determine who would serve as regent if the King and Crown Princess were to die before Estelle turns 18.
Art. 5. Should the Royal House become extinct, the Riksdag elects a Regent to perform the duties of Head of State until further notice. The Riksdag elects a Deputy Regent at the same time.
The same applies if the King or Queen who is Head of State dies or abdicates and the heir to the throne has not yet reached the age of eighteen.
I suspect his regency comment was not referring to the long-term regency that would be necessary in the event of Estelle becoming Queen during her minority, but to the short-term regency that would be needed if the King and Crown Princess were simultaneously temporarily unavailable (for example, because of illness or travel), in which case Prince Carl Philip would automatically be the regent ad interim.
Art. 4. If the King or Queen who is Head of State is not in a position to perform his or her duties, the member of the Royal House in line under the order of succession and able to do so shall assume and perform the duties of Head of State in the capacity of Regent ad interim.
In the case of a Queen Estelle who is under 18, I would hope that Parliament would appoint Prince Daniel or Queen Silvia to the regency, as most other European monarchies would do, rather than bypassing them both for Prince Carl Philip who has never been a full-time working royal.