Either restore and reinvigorate or remove... don't retain something just to retain it.
That said, restore.
Restoring will never extend its life long enough unless we effectively rebuild it, which is borderline impossible.
As much as I'd love to live in a pie-in-the-sky world where the High Level's capacity and durability are enough for a 2M+ people metro, reality is harsher.
The Gondola is cool and will be a great transit addition, but will never replace an actual bridge, car usage percentages might fall, but unless we become Berlin within the next 25 years, with the populational growth, traffic will increase substantially and the High Level will be even more of a liability for emergency services and a chokepoint bus routes and overall traffic, especially considering the densification of Old Strathcona and Garneau.
Not to mention the potential to become a much more comfortable and safe pedestrian and bicycle routes, allow for high-volume transit modes and even potentially HSR (or any heavy rail altogether).
And there's still the potential to create another landmark, which can become a bit of a tourist draw and pile up with the host of new cool projects for Downtown and Old Strathcona (Gondola, Pedestrian Bridge, Warehouse District Park, VLW LRT...).
If we are to keep the current bridge (which I agree we should do, as it is a very significant part of our history) it no longer can be the main connection between the two densest areas of a major metro. Restore, yes, but repurpose as part of the Highline Park project, provide space for ERRS service expansion (if and when they have capacity), use it another way to facilitate active transportation... Denying its obsolescence for the current purpose will only prolong the suffering and make the solution more expensive.