It's only going to continue to go up. It is THE hobby card. Everyone wants one. There isn't a single card that is more iconic in this hobby other than possibly the mostly unobtainable Honus Wagner, but even then I think the Mantle is still more iconic.
I recently paid $45k for one in an Authentic slab though, so perhaps I'm biased. But I obviously believe in the card to spend that much on an altered? copy of it (though upon close examination, I haven't found any hard evidence of it actually having been altered yet).
