First of all going from FO to Capt is an upgrade. Moving to the widebody is a transition. It’s a different plane and does a different kind of flying, nothing more, nothing less. At Hawaiian (as with most airlines) you’ll find junior and senior pilots on most airplanes. As for airplane assignments HA newhires go where there’s a need and vacancies. Some go 717, some go 321, some 330. When I was hired we bid for available slots. Since I was junior in my class (based on my SS#) I got the last pick which was the 717 but I could have just as easily gotten the 767 or 330.
As for the 787s they won’t be here till 2020 so we’ve got some time. Despite what you think most pilots with any experience are really less impressed with shiny new metal and care more about the particulars and how that will effect their quality of life. Pilots look at pay, destinations and trip duration. I for example plan on staying on the 717 for as long as they’re here (or I retire, whichever comes first). It’s the smallest of the fleet and pays the least but it allows me to be home every night and I enjoy the flying. While it’s always cool to add another Type to your license after a month the “coolness” wears off and it’s just another plane. Until they announce the details no one is lining up for anything. They actually posted an opening for 787 Fleet Capt to start working on the training program. There were no applicants.