I am sure someone will eventually hire him again. I mean we all saw how he did at Manchester United, and for some reason Leverkusen still believed he could be the next one after Xabi leaves, we all knew that was a mistake but they did it anyway. So that means we are going to see him end up with another job like that. Leverkusen realized he wasn't the guy to do it after just three games or something, and I am sure some other team will regret getting him too.
But when you are at this high level and have this much brand power in your name, you end up getting jobs. Look at Mourinho for example, he was one of the best at his time, but for the past 5-6 seasons he has been nothing but a failure, sure he won conference league, but seriously nothing else and at leagues he sucks. So it's true that we should probably expect similar stuff for ETH. Or he could just go to Arabian league and make money.
Obviously someone will hire him, but not any team at the top, that is for sure. No team that is a big name or can afford to pay him a lot, will ever hire him until he proves himself again. He could go to some midlevel team or even maybe outside of big five leagues at this point.
If he does that, then he could find a job in either lower levels of big five, or higher levels of some other lower league, in that case he will have a chance to prove himself all over again. If he does that, then yeah he is going to end up with a better result, it should not be a problem at all for him. However, if he goes to a worse club and does bad even there? Then I am pretty sure that his downwards movement will make him not be hired eventually.