I don't think the NHL will expand past 32 teams for a very long time, so scratch expansion.
As for relocation, before Salt Lake City to be considered, they would need an NHL ready arena at least in the works to be built. Apparently the Vivint Smart Home Arena just underwent a renovation, so it's unlikely a new arena will be built in the foreseeable future. I don't think the NHL wants the headache of a team playing in a basketball arena in which there are issues with obstructive seating (think Phoenix and Brooklyn as two recent examples).
As for western relocation cities, they are behind Houston, Portland and Kansas City for cities the NHL would want to be in over Salt Lake City due to size, NHL ready arenas, and in the case of KC, lack of NBA competition.
I would think if Utah was craving another pro team, they'd likely try to get an NFL team.
Stranger things have happened, however, I think it'll be quite a while before Salt Lake City would be a favourite for an NHL team.