What he says: I’m fine.
What he means: Is Bill Cipher really gone forever? His last words sounded like a plea to the ancient Aztec God of Death Xolotl. Is Bill Cipher actually Xolotl? Or… is Xolotl the real mastermind behind Bill’s Dimension-conquering motives? Is Xolotl supposed to be the true villain of Gravity Falls? Has the triangle demon SUMMONED his master as one last attempt to bring the apocalypse to our dimension?