In hindsight, HA probably should have split the original order between Airbus and Boeing - A332 for immediate capacity lift and 787-8 or 787-9 for long term growth. They would be getting their 787s right about now.
Instead, HA went for A332 + A358, which became A332 + A338, and now they have this vexing issue with potential value and financing cost for A338.
Unfortunately with an airline the scale of HA, a split wb fleet would not be in their best interest. If they had twice as many planes, maybe...
Staying on topic, I think the real issue with the A338 (or any other potential wb currently) at HA lies within 2 issues:
1. Size - This has been what HA has desired since it originally placed their wb order with Airbus. A332/A358 - economics of the type, size of the model. IIRC, when asked why not the A333, Dunkerly said it was bigger than the airline needed and desired, same as to the A359. This was readily apparent and affirmed when the A358 was known to be dead and HA held out fr a different option from Airbus and did not convert to the A359. In fact when the announcement for the A338 finally came, Dunkerly had mentioned that AB had assured the aircraft could make it HNL-London. Though doubtful it would be in HA's current configuration, the assurance was verbally given and again they chose the 338 specifically and not the 339 citing size yet again. The size of HA as a whole also would encourage the smaller/lighter model to save on crew/airport fees which in the grand scheme of things may not be much, but to a small airline can make a big difference.
2. Range - We can bend it any way we like, but ultimately HA ordered the A358 for 1 thing only - range. Dunkerly had his eyes set on London and I don't think that desire has changed. I believe the only reason they selected the A338 was because of the range assurances from AB. It was a long shot in HAs dense seat layout that it would happen, but if AB couldn't deliver HA again had nothing to lose. This interview stating HA wants 12-15 hour flights in its future more than doubles down on it's desire for an aircraft with the legs in the size range it currently has.
We all know HA is a niche airline and needs/has sought niche aircraft. Unfortunately in the current state of aviation, HA has terribly limited options. "Non-stop to Hawaii" is their niche and they've been relatively successful despite the anet myth that Hawaii flying is a money pit. HAs relationship with Airbus is akin to their previous relationship with Douglas. I don't see them jumping unless 'it' hits the fan. As much as I would love to see Pualani on a 787, I don't think it would be the best choice for HA at this time.
If Airbus can't/won't give the range that HA desires in the 338, the only 2 options I see are 1. Diverting payments into the A321 balance, or maybe adding a 330 or two (85% chance). or 2. Taking a huge jump from its intended business model and taking the 359 (15% chance).
Bringing Boeing into the fold to look at their options is a no lose scenario for them.