Interesting discussion. e-Bay indicates that camping gear can last 50 years and that's the bulk of my "survival" gear. Some of my camping gear that could still be around because they are no-tech or low-tech and sturdy:

knives
axes (Gransfors Bruks)
Thermette/Kelly Kettle
cast iron dutch ovens and grill
waxed cotton packs and bags
Coleman stainless cooler and jug
candle lanterns
campstoves
steel chuck box

Technology is advancing so rapidly I'd guess my flashlights and headlamps may not have batteries available for them in 50 years.

Super-lightweight fabrics in tents, clothes and packs probably won't prove very enduring, unless they are coddled in someone's attic.

My plastic Aqua-tiners are quite durable but I'd think they are less likely to be retained.