Indeed! And on top of that: Even the FP1 can read and use a 1TB microSD card as demonstrated by @urs_lesse. To sum it up: I would not worry too much about that at the moment, 2TB are very likely supported, but of course nobody can say for sure before we even have such a card.
Beware: Just because one of those (hypothetical) cards does not work in the phone does not mean it’s because of the capacity. There are some known issues with certain brands on the FP4, for example.