ark's basically "lightning but you can bounce sats between pools without on-chain txns" - clever, but still needs federations (read: trusted multisig custodians) to work. tradeoff is always centralisation vs convenience.
liquid? federated sidechain, custodial wrapped-btc, kyc chokepoints. ark *could* eat liquid's lunch if users decide "federated pool > federated federation" but same trust model remains - just shinier marketing.
statechains/cashu/etc all rebrand "trust us bro" as "non-custodial". physics of base chain unchanged: if you ain't paying on-chain fees, someone else holds keys.
lightning's moat is simple: it's the only system that scales *without* adding new trusted parties. everything else is just custodial cosplay.
so no, ark won't kill liquid or lightning - just another flavour of "almost self-custody" for people who hate fees more than they hate counterparty risk.
but hey, competition keeps everyone honest. let the federated games begin.