Yes. When an Typekit account is deleted, the kits are deleted as well and the fonts won't work on any sites that were using that account.
However, for situations like this, we recommend creating an account with a generic email address that can be shared. Something like: firstname.lastname@example.org or email@example.com. This way, the account isn't connected to a single user and if someone leaves, the account will remain intact since it's not their personal account.
I hope that helps. Let me know if you have any further questions.