Or is there another .conf file somewhere that's updated dynamically?
Yes peers.dat
OK, so a bunch of people get together and launch a currency. They create a wallet which has a .conf file containing some initial nodes which, presumably, correspond to hosts under their control. They make the wallet available for download.
People start to use it and their software discovers other nodes which it stores in peers.dat. Is that correct?
Now, let us assume that the developers then abandon that currency and over time stop running nodes on the hosts listed in the .conf file.
If I have this right in my mind, those with wallets already created can continue with transactions (because their software has already discovered and recorded other nodes) but someone downloading and installing the software from scratch wouldn't be able to get started because the nodes in the .conf file no longer exist.
So unless someone else decided to "take over" (in a figurative sense) and update the software then over time you'd get very few new users.
Yes once created even the owners can't stop it.