AFAICS, there's no announcement if their wallet is under development or stop to operate.
In your post, assume your information is correct, stop development of a wallet does not mean it is something big. At the moment, if they stop development their wallet, you don't lose your cryptocurrency there and you can move your crypto to other wallets.
Their
FAQ shows that Argent wallet is non custodial.
Nope, non custodial they wrote in their sites is just a gimmick.
Read below, the conclusion is you're trusting your wallet with hardware wallet, device, other people and the site itself. They didn't give your seed phrase, so you can't recover your coins in other wallet.
Argent is the first non-custodial wallet with no seed phrase and no complexity. With your Argent Vault, enjoy peace of mind through locking and unlocking your account, auto blocking transactions, and setting trusted contacts. And your Argent zkSync account offers the best of Ethereum, at a fraction of the cost.
Argent is also unique for making decentralized apps like Uniswap, Aave, and Compound for L1 and Yearn, Lido, and ZigZag for L2 as accessible as Whatsapp.
No more writing down recovery phrases and passwords. Just ask your guardians for help. You need the majority of your guardians to approve a recovery.
What are guardians?
Guardians are people and devices you choose to help keep your wallet even more secure.
Guardians NEVER have access to your cryptocurrency.
You can ask them to help you:
Lock your wallet
Approve a wallet recovery
Approve an untrusted transaction
Types of guardian
A hardware wallet or other device (e.g. another phone) that you own yourself.
A person you’ve selected because you trust them (e.g. a friend or family member).
A third party service. An example is the default Argent guardian, which uses 2-factor authentication.