There are about 57 cases of Covid-19 in Canada, mostly in Ontario and BC.

The con itself wasn't cancelled, Jesse just cancelled his appearance (as far as I know).

As for filming around Melissa's pregnancy: Jesse mentioned there was only going to be a few weeks turnaround from the end of S5 to filming the beginning of S6 at another con a few weeks ago.

Assuming the filming will go until middle or end of June, they should have most of the first batch of episodes done.