Talk, Talk, Talk
Start having conversations with your parents about how they'd like to spend their future. Do they want to grow old in place, or would they consider moving closer to you? How will they get around once they stop driving? Check out their health insurance and what they're entitled to from the government (Social Security and Medicare or Medicaid) so you have an idea of how they'll be covered.
A financial planner who specializes in the elderly can help you figure out if supplementary health or long-term care insurance makes sense and whether your parents—or you and your siblings—can afford it.