Moving the Coyotes to Houston would make sense. It's the 6th biggest city in North America, and the Dallas Stars have been a stable franchise for a long time.
As much as the NHL's fought to keep them in Phoenix, they need a new arena even more badly than the Sens do. Even so, every effort to get someone else to pay to build them one has failed so far. Eventually, if you can't make any headway and you're losing bucketfuls of money every year, a deep-pocketed owner in an even bigger city has to seem like the way to go.
From the NHL's perspective, it'd keep the team in the southern US and it doesn't upset divisional balance. Seattle would move into their spot in the Pacific division, and Houston would fill the empty spot in the Central division, alongside their new divisional rivals the Dallas Stars.