Ottawa is a relatively small city (in continental, not Canadian context), and the need for two similar sized performance venues (CTC and LeBreton Flats) in a city like Ottawa is questionable. I've been to a Senators game at the CTC (staying in a downtown hotel), and, the drive out there was a pain (let alone the parking situation). It will be very difficult for the CTC to compete for high profile concerts.
The CTC may hang on a few years, but, demolition will happen at some point.
We had a similar situation in Moncton when the Avenir Centre opened downtown. Happily the old Coliseum is paired with an Agrena facility used for regional trade shows, and the facility remains profitable. They use the arena space to supplement the floor space of the agrena. They've maintained the ice plant, and the rink remains active mostly for house league and beer league hockey.
Is there any possibility the CTC could be repurposed for regional trade shows????