Rabbit pairs and passing away.

I know it is a bit of a morbid topic but I was just wondering about this.

My rabbits are brother and sister, and have spent pretty much every second of their lives together apart from when they go to the vets.

They are 8 at the end of this May, and everywhere has different life expectancies...from 5-12+ usually but they are still very healthy and active.

They are very close to one another and it is just I'm worried that if one of them dies then the other will be very lonely, nothing that human contact could make up for. I'm just wondering what is the best thing to do in these situations? Rehome them with another rabbit or just let them live out their days in familar surroundings?

My lovely chocolate lop Halle Berry died in her sleep 2 months ago. Her pal Daisy Duke and her were inseperable for 5yrs. They spent all their time with each other snuggled up together and grooming.
I thought I would get a pal for Daisy, but I am having a nightmare bonding with the new one (see Bonding going very badly). If I had a magic wand, I would like to see my new rabbit in a new home rather than put Daisy thru all this trauma as I think she may be better on her own than going thru this stress. Everyone says a pal is always a good idea though.