What makes their calendar so fascinating is that they weren't predicting the future at all in a soothsayer/prophet kind of way. Sure, they had a religious side and did the whole bloody sacrifice thing and called out to the gods like nobody's business, but they kept their math and astronomy separate from that. And they had things like eclipses and alignments and processions and all that worked out in crazy levels of detail - levels we've only really begun to understand in the last decade or two (with the aid of computers).
It's also worth pointing out that the Spanish arrived several centuries after the collapse of the Mayan empire.The Mayan calendar only marked yesterday as the end, and it was the lack of anything going beyond that date that had people jumping to conclusions. But the
recently discovered calendar workshop site paints a different picture. The reason nothing went beyond yesterday is more likely because that was the end of that cycle, and they hadn't yet finished the next one before their civilization fell. Evidence suggests that they were continuing to work out the solstices, eclipses, alignments, and so on for several more baktuns.
I guess it's back to planning for the zombie apocalypse and natural disasters
