Sad to see CLE go, but I think most of us who keep up with the airlines saw this coming. Not sure how many on here remember, but CLE was a United hub back in the day long before they inherited it from Continental. From about 1972 to 1986, it was a decently sized hub with 107 departures at its peak. I know they ran a DC-10 on SFO-CLE for a few years.
Here is a link with statistics for those interested.
I feel for the employees, few hubs seem to last forever. With the AA/US merger, my guess is PHX will be next. I don't think it'll be dismantled, but I do think it will become a shell of its former self.
While not pledging to eliminate all 50-seat flying like DL, it's no secret Jeff the creeper Smisek wants to dramatically cut down on them, seeing as CLE is mostly a 50-seat or less hub, who knows.