Upvote:2
The relevant paragraphs from the Catechism should answer your question, as they cover all categories. They are CCC 1257-1261. Unbaptized Protestants should fall into the category discussed in paragraph 1260
"Since Christ died for all, and since all men are in fact called to one and the same destiny, which is divine, we must hold that the Holy Spirit offers to all the possibility of being made partakers, in a way known to God, of the Paschal mystery."63 Every man who is ignorant of the Gospel of Christ and of his Church, but seeks the truth and does the will of God in accordance with his understanding of it, can be saved. It may be supposed that such persons would have desired Baptism explicitly if they had known its necessity.
If a Protestant is ignorant of the Gospel of Christ or of the (Catholic) Church, yet seeks the truth and does God's will insofar as he understands it, it is possible that he could be covered under an implicit Baptism of Desire.
The more an unbaptized Protestant learns about the Gospel and about the Church, the less likely it becomes that he would have sufficient ignorance to be plausibly supposed to have an implicit Baptism of Desire.
The Baptism of Desire is explained in 1259
For catechumens who die before their Baptism, their explicit desire to receive it, together with repentance for their sins, and charity, assures them the salvation that they were not able to receive through the sacrament.
Generally, catechumens are seeking baptism explicitly, and thus have an explicit Baptism of Desire. But, one who is ignorant and would have desired Baptism had he not been ignorant may be saved by an implicit Baptism of Desire.
To answer your question directly: yes, technically, an unbaptized Protestant can go to heaven according to Catholic Theology, but the faithful Catholic would consider it very unlikely that persons in this category are really invincibly ignorant, and thus consider it very unlikely that such individuals will enter paradise.