It probably depends the architecture of the dapp, that’s an advantage of the IC. If the project creates a canister per user - e.g. in which the user’s data are saved - and let users assign additional controllers to these smart contract, then the main project disappearing does not mean the users lost their assets.
e.g. in my project Juno, the main app is “just” a facilitator, each user gets a personal canister to which they can add additional controllers. Likewise for other canisters they create. So if the main app would ever disappear (not the plan, just an example 
), they would still have everything because they control their smart contracts, they own their data (https://juno.build/docs/architecture).
Papyrs, OpenChat, Hot or Not (I think) use that architecture. In Papyrs it’s not yet possible to add extra controllets but, if the project would ever been discontinued, I would offer such a feature first.
Makes sense?