Any old Pan Am(original) Worldpass members who had miles moved to Delta's program?

I was told we can be easily spotted by the first 4 digits of our current Delta member#, which is 4000.

When Pan Am went under, I had close to 300,000 Worldpass miles. Fortunately, they were all safely and automatically stored in my new Delta FF account. In fact, I still have some of those miles left.(about 25000)

Back then, I didn't really like Delta that much. However, what they did with the Pan Am members was really nice. I became a very loyal Delta flyer, even today.

The reason I brought up this old issue is because some of today's airlines don't seem that stable. If one of them goes down, can we still expect the airline that buys the bankrupt airline to honor our miles? I do have some substantial miles in a couple of the troubled airlines...