Seattle and Vegas will help the USA enrollment numbers if they build the youth programs in those areas. You look at a place like Arizona when the Coyotes came in their was hardly any hockey. Now youth hockey has exploded, a D1 team was added (ASU), and an AHL team relocated to Tucson. Hopefully Seattle and Vegas have the same success along with better success with less attendance/arena issues.
Another step forward would be a few more new D1 programs...such as Illinois, Nebraska, and Iowa. College grads are so attached to their alumni in the US. I know a few die hard PSU alum that could care less about hockey until PSU added a team and now they have their kids skating and attending/donating to PSU hockey.