The main issue for any team right now is arena and arena location. Arenas had been on the outskirts for a long time but in the 90’s they started to move either further out for cheep land and a larger footprint or downtown for easier access but slightly undersized to keep costs down.
It turns out that the slightly undersized downtown arena is by far the best option. The oversized area out in the boonies has been an absolute disaster for teams stuck with it. If you look at any team with chronic issues, most of them have these oversized areas a long way from downtown.
That said Houston is the obvious target. It’s the 4th largest city in the US and the 9th largest CSA (Common Statistical Area), the largest CSA in the US that currently doesn’t have a team. Seattle is in the 13th largest CSA in the US. (Unlike Metropolitan Statistical Area CSA’s can overlap and they are not as tightly coupled as Metro Area but still share a lot of media and economic activity, commuters, etc. For cities that are part of one it’s a good way to look at the potential fans a team can reach in it’s area.)
After that the largest CSA/MSA that don’t have an NHL team are Atlanta (6.6 million in it’s CSA) Cleveland (3.5 million in it’s CSA) Orlando (3.3 million in it’s CSA), San Diego (3.3 million in it’s MSA) and Portland (3.2 million in it’s CSA). So for US relocation these would seem to be the highest priority.
Houston – seems like a perfect fit for a Phoenix move, but I think the NHL wants to be in Phoenix (4.7 million), but they must have a downtown arena.
Atlanta – yah yah yah, but the problems they had were primarily Ownership/Arena. With the right arena and owners I think the NHL jumps at the chance to get back there.
Quebec – arena and established hockey market so it’s an easy move.
Second Toronto team – they’d need to figure out an arena and owner but I think there is enough demand, not just from fans who can’t get Leaf tickets, but the sports networks who own 2/3 of the Leafs would love more Toronto games to broadcast.
Cleveland isn’t growing but it’s more traditional part of the US for hockey, which is probably why you see it mentioned a lot. Could be an interesting relocation target
Orlando I’d think they want to Stabilize Florida (which is in the Miami CSA) but maybe with a better arena location it’d be a good place for the Panthers. Also, Miami could have some issues going forward as it struggles with flooding from rising sea levels so it may not grow as rapidly going forward.
I’ve never really thought about San Diego but I wonder if it could be one of those off the radar cities that could cultivate a good hockey market but I can’t see any current western team moving there.
Portland seems like a good place for a western relocation but other than Phoenix I can’t see any current western team moving. Also, close enough to Seattle that the NHL may not want to go there yet.