Had a final interview for a manager position at a large Canadian firm and didn't talk about salary at all. I discussed in brief salary expectations during my first phone interview with the recruiter.
Is it usual for this to happen?
Sometimes it does, sometimes it doesn't.
It means they'll make you an offer if you got the job. You can then negotiate from there.
It's also possible they decided they weren't interested after all and saw no need to discuss salary.
In either case, all you can do is wait.
Yes, this is normal.
Interviews are for one purpose - to determine whether you want to work for the company, and whether the company wants to work with you (in other words, is there a good fit between you and the position/team). Salary expectations are a part of what makes a good fit, but it sounds like you've already discussed that.
After a good fit been established, the company and you enter the negotiations phase, where you discuss your compensation. Until the company has determined you're a good fit, there's no point in negotiating.
Sometimes, a final interview can transition into a negotiation, but this is not a requirement. If there are more people they need to interview before picking the best candidate, it's simply too early to spend energy on negotiation.