From all of the things they've announced, it sounds to me like their plan to make money is by competing with Adobe and others to be the main DAM (digital asset manager) for companies. Companies will pay them to store their brand guidelines, approved imagery, and more in Canva so their non-designer employees can use them and create things like slides and ads with approved branding materials easily. Meanwhile the designer employees can use Affinity to create the high quality imagery and source files that everyone else uses.
If they can break into that market, it's a big one.