They are. But in my opinion, the 737 or A320 family are not going to be good solutions for the interisland fleet. True the 737-600 would have a lot in common with the 737-700s, but the costs of operating them in the interisland market, as aircraft designed for longer flights than exist within Hawaii, would put them at a serious disadvantage to Hawaiian, with 717s designed for short flights.
I have heard that Aloha has been in discussions with BAE Systems for the Avro RJX 100, and they are also going to me monitoring Hawaiian's success with the 717. I suspect the final decision will be one of these two aircraft.