What happens when Ledger or any hardware manufacturer goes bankrupt and exploits are found and the developers are not there to plug the holes? (Export seed to Electrum?)
Nothing lasts forever, so one should not expect Ledger to always exist. In the event that Ledger stops supporting its devices, anyone who doesn't feel safe will look for an alternative.
Yes; you just get a new device and transfer the coins. You can also just trash the old device and import your backed-up seed into a new wallet. I recently thought about this and maybe it helps people think of hardware wallets a bit differently: think of the device mostly as a signer. Don't rely on it not breaking, not getting lost or not ceasing to turn on, to be able to access your coins; instead, rely on your seed backup(s) and use the device as a convenient way to utilize said seed in everyday scenarios.