True, but if it was extinct, it would have to be a pretty monstrously wild palm tree, and I think that the mangroves already inhabit the "monstrously wild" category.
There's also the possibility Mojang will make something new up, for example, a tree with non-flammable wood (like the Crimson & Warped fungi) from many eons ago, with black bark and massive proportions.
In my personal opinion, a black wood is long overdue, so I'm hoping they go for something along the above lines.