As with any franchise in any league, the success of a QMJHL team in St John's has everything to do with the ownership, and nothing to do with the city's history in the league.
Although the Fog Devils were not as popular as any AHL franchise has been, their attendance was consistently above 3500, a number that would place them solidly in the Top 5 for attendance this season.
Yes, they would have higher travel costs, but that is a moot point when considering which league they should be in, given that travel costs would be an issue for a St John's franchise whether it was in the ECHL, AHL, or QMJHL. In fact, it's less of an issue for a QMJHL team, given that teams would not have to fly from the US.
The franchise relocation that would make the most sense seems to be Acadie-Bathurst, which is in the Maritimes division, and struggling badly with attendance. It's lost money for many years, and is presently co-owned by a collective of local business and NHLers who are alumnus of the Titan. Those types of ownership arrangements do not last long, as they are driven by nostalgia, the novelty of which wears thin after a few seasons.