Would a flight to St John's really be a good thing? There could only be limited demand between the two cities and neither Cork nor St John's can offer massive opportunities for onward connection. I'd worry that it could just be a false dawn that could discourage real transatlantic opportunities.
If it was a one-stop connection to Toronto, like their Dublin service is, it might improve matters, but that suffers by sticking extra capacity into the limited market from St Johns to Toronto.
Perhaps a stop in Halifax on the way to Toronto might open up more connection opportunities and link to a larger market in Canada.
On the plus side for St John's, it's only around 30 minutes more flying time than a flight to Tenerife.