Have you spoken with them about their own wishes? I would try (repeatedly, if necessary) to have those conversations.
You should have a durable POA, be a medical proxy, and get them to think about what end-of-life measures they want taken.
If they havent prepaid funeral expenses, that would be a good thing for them to consideralthough I know nobody wants to think about their own funeral, lol. Still, having it done means less stress for the surviving family members.
If you can afford it, you might want to consult with an elder law attorney and/or a geriatric care manager (actually, your parents should pay for these services, but you might need to consult them in private first). At the very least, start doing some online research into elder law/services, both in general, and for whats available in your area.
They will die. Its a given. Hopefully neither will be very sick and helpless much before then. But it is a distinct possibly, and the more you do now to prepare yourself (and them), the better.
Its also vital that, as you will probably take on more management of their affairs, that you learn to set boundaries with the other stuff they seem to always want you to do. No heavy lifting. No moving furniture around. No cleaning out sheds. You will need your energy for other things. Learn to separate wants from needs.
When I was taking care of my MIL, I used to hang out at this site a lot, but its become rather quiet. No experts, just caregivers exchanging stories and advice.
Heres another site for caregivers that looks pretty good.
Good luck, and keep us posted!