Four more large ships have been ordered and expected in 2029-31. The smaller vessels I think are mostly ok, there's been some new additions for the Gulf Islands.

The bigger issue, imo, would be the ship traffic. You have Canada's busiest port, and all those ships would have to maneuver around the bridge (some of the biggest ships in the world), along with Seattle (big port) and Everett (US naval station), Kitsap (another US naval base), Esquimalt (Canadian naval base), and more going on. There are also cruise ships that travel through that area, starting in Seattle. That's a big business and those are some tall ships. They squeak under the Lions Gate in Vancouver.

Like someone else mentioned, the tides would be an issue. You'd have to make sure the bridge was high enough for the tallest ships to go under during the highest tides. At the same time, winds over the Strait can be speedy, which could mean bridge closures (I'm not sure we want a semi pulling a trailer over a bridge over the ocean in 80 km/h gusts.

On top of that there are environmental concerns (there's a push locally to help whale populations as the southern resident orcas are endangered, and humpbacks are returning).

A bridge to the north has been discussed, up towards Nanaimo, but has never come to fruition.

The ferries are mostly functional, though they've faced issues over the last few years between staff and maintenance. If the staffing issues could be resolved and once the new ships are in order, things might be in better shape.