Short answer. Usually no. The rule allows the heirs of the deceased to be substituted without requiring the appointment of an executor or administrator, and the court may appoint a guardian ad litem for any minor heirs. That keeps the case moving without a separate estate proceeding.
What the law says
The heirs of the deceased may be allowed to be substituted for the deceased, without requiring the appointment of an executor or administrator and the court may appoint a guardian ad litem for the minor heirs.
Rule 3, Section 16 — Death of party; duty of counsel. Read the full provision →
Substitution without a separate estate proceeding
Opening a proceeding to have an executor or administrator appointed takes time and money, and where the only reason for it would be to continue a case already pending, the rule dispenses with the requirement. The heirs may be allowed to be substituted for the deceased without requiring that appointment. The word allowed is doing work there: this is something the court permits rather than something that happens by itself, so substitution still has to be sought and ordered rather than simply assumed by the family.
Minor heirs are provided for
Where some of the heirs are minors, the absence of an administrator does not leave them unrepresented in the case. The same provision lets the court appoint a guardian ad litem for the minor heirs. That is an appointment made for the purposes of the litigation, which is a narrower thing than a general guardianship over a minor's person or property. It exists so the case can proceed with someone answerable for the minors' interests in it, without forcing the family into a separate and larger proceeding.
When an administrator is still needed
The rule keeps a fallback for cases where substitution does not happen. The court orders the legal representative or representatives to appear and be substituted within a period of thirty days from notice. If no legal representative is named by the counsel for the deceased party, or the one named fails to appear within the specified period, the court may order the opposing party, within a specified time, to procure the appointment of an executor or administrator, who shall immediately appear for and on behalf of the deceased. So the appointment becomes necessary when the heirs do not step forward.
The first step, and the timing
None of this starts until the death is reported. It is the duty of the deceased party's counsel to inform the court within thirty days after the death and to give the name and address of the legal representative or representatives, and failure to comply is a ground for disciplinary action. Heirs who want to be substituted are better off raising it themselves than waiting, because the periods in the rule run from notice, and a case can move on while nobody is speaking for the deceased party.