There's no reason for people to adopt it.
If the prime POW proves to be demonstratably better than SHA256d, it could be adopted by Bitcoin with a hardfork.
Things like this (enhancement to a specific technical detail) should be done as testnet branches - as proposed changes to Bitcoin.

Without a hope of adoption, Bitcoin and forks function in a pyramid: when people get tired of it, the ones stuck with the coins in the end lose out.
Bitcoin is different because its innovation makes it possible to achieve a status quo where everyone wins (by having a usable decentralized currency).
Any new system would need to have a viable way to compete with Bitcoin (ie, something Bitcoin couldn't just adopt as an improvement).

Examples of altcoins that don't function as scams:

• Tonal Bitcoin: Compatible with BTC, uses the same blockchain. Whether it succeeds or fails, nobody loses value so long as Bitcoin as a whole doesn't fail.
• Namecoin: Not a currency, but a domain name system.
• PPCoin: Uses proof-of-stake instead of proof-of-work; arguably this is so fundamentally different that Bitcoin could not adopt it. Note that last I heard, PPCoin was being used as a scamcoin despite this, however, and there were some major problems with centralization/security tradeoffs.
• Freicoin: Features demurrage, which trades the "why spend it?" problem for a new "why acquire it?" problem. It would violate Bitcoin's social contract to make an economic change like this.