If pi is indeed normal (whether proven or not), that would never happen. A normal number, by definition, contains an even distribution of digits. There would be no "last 9" because there would have to be more after to satisfy the distribution. Basically, the count of all nines must be the same as the nine other numbers, as the number of digits goes to infinity.

Even if the first million digits of some unnamed number were all nines (with no more afterward), it would not be normal because the distribution of nines, as the number of digits goes to infinity, would go down.