Can the Terrestrial Paradise become Limbo for someone like Virgil?
In canto 28 of Purgatory, Virgil is inside of the Terrestrial Paradise along with Dante and Statius. This seems like an odd thing to happen, since Virgil normally dwells in Limbo, which is in hell. Limbo is a place in hell that is specifically for what Dante calls the “virtuous pagans.” Virgil, along with the likes of Homer, Socrates, Plato and Aristotle are all within this circle of hell. They are not being tortured but they are not enjoying themselves either. They are merely in an eternal state of never leaving where they are and having no hope of leaving where they are. The Terrestrial Paradise, for someone who cannot enter the true Paradise, would seem to be a very similar situation. It would be a place where you would have no hope of leaving, you would not be tortured. You would however enjoy yourself. Limbo and the Terrestrial Paradise of quite similar, in those senses at least.
Does anyone ever stay in the Terrestrial Paradise? From reading Purgatory, it seems as though no one stays there permanently. It could be argued that Matelda stays there forever, but there is definitely not a focus in Dante on the “people who stay in the Terrestrial Paradise” as there is for people in any circle of hell, purgatory or paradise. If no one stays in the Terrestrial Paradise, which I would say seems quite likely, then the purpose of the Terrestrial Paradise is to make a person forget all of their sin in the river of Lethe while reminding them of their good deeds in the waters of the Eunoe which prepares them for the Celestial Paradise. If this is the only point of the Terrestrial Paradise, then it would not make any sense to have it become Limbo for any virtuous Pagan.
It also would be odd if a virtuous pagan dwelt in the Terrestrial Paradise as if it were a Limbo because the Terrestrial Paradise is located at the top of the mountain of Purgatory. For a person to enter the Terrestrial Paradise, they must purge themselves of their sins (in other words, they must conform their wills to what is good). This seems to be something that a virtuous pagan would at least be capable of doing. The problem here is that to enter the mountain of Purgatory, one must have been saved by Jesus Christ.
But somehow, Virgil entered Purgatory, and he entered the Terrestrial paradise. This is because he believed in Jesus, after his death. Virgil could not be saved from eternal damnation because he did not believe in Jesus Christ as Savior and Lord during his life, but he is not disqualified from entering Purgatory or the Terrestrial Paradise in this case because he is no longer with any fault. His fault of not having faith in Jesus Christ is condemning but not restricting when he is called upon by God (or Beatrice in this case) to act.