Great question.

First, since it's a 2-of-4 multisig wallet. Nunchuk going out of business won't affect the owner as they still hold three keys and are always in full control of their funds. They can use old versions of Nunchuk which are available as APKs, or can be compiled from source. Alternatively they can use other wallets such as Sparrow to recover their Nunchuk wallet and move their funds. If the owner is still alive, this would be our #1 recommendation.

Second, if that does happen we will do our best to (a) have a long wind-down period and (b) notify our users well in advance, so that they have all the information they need to move their funds.

Third, regarding the inheritance plan, we recommend our users to use a rolling short timelock. In the unlikely event that Nunchuk ceases to exist and the owner has passed away, the short timelock (we recommend a 1- or 2-year timelock) would allow the beneficiary to react in a timely manner and claim their inheritance sooner rather than later.

Hope this answers your question.