Pretty much any BTC spinoff can and has forked the chain, auto-airdropping their coin to all BTC holders. You don't even have to go that far though, a coin could easily have a smart-contract style method of signing a message with your BTC private key, and get granted an equivalent in free starter coins.

Coins are also becoming increasingly fungible ... there's more exchanges every day, shapeshift/changelly style portals, and lightning adding atomic swaps across chains.

More importantly though, whether this is the end of the early adopter phase, or just a "late end of early adoption" phase... most people coming in won't want a coin with a lot of baggage and most of the value hoarded into a few accounts (inheriting BTC's chain could be seen as a negative there; and BCH's speedmining run didn't help it out).