While it is just wishful thinking, it would, when you stop to think of it, in many ways make sense for DL to decrease it's intra-Asia flights from NRT, if JL joins SkyTeam and closely partners with DL (just like DL has done e.g. on the SGN flight now with VN joining ST), and instead build out HNL as a US-Asia gateway. A number of benefits it would bring:
* connecting in the US
* creating more jobs in America (vs. in Japan for NRT connections), so DL doing its patriotic duty
* HNL airport is huge and greatly underutilized - DL could likely get a notably lower $ per passenger cost vs. at NRT as the HI government would likely be happy to subsidize it for creating more jobs and bringing more tourists (esp. if DL also brings back NW's former pilot training facility and reservations call centre to HNL, which may make sense as a package deal and if HNL is becoming a DL hub)
* DL could think "out of the box" and upsell 1/2/3/4/5 day layover packages in HNL for connections to Asia, that I bet would be rather popular (I know if I didn't live here I would prefer to connect through HNL and stay a few days here on the way) and another revenue generator
* US - HNL flights are domestic so DL would save on the in-flight catering and services and make money on selling the food, drinks, &c. (at least for flights from west coast and SLC, as from MSP/ATL/DTW direct flights the food is included due to the length of the flight) - that would only need to be done for the HNL - Asia portion, not for HNL - mainland US portion
* HNL is a very pleasant airport to stay in and connect in
* most direct connecting route from US to SE Asia destinations like SIN, KUL, BKK, SGN, MNL, CAN, TPE, HKG, PVG, etc., as well as to Australia (though not sure if DL would want to compete with Hawaiian Airlines, Quantas, JetStar, Air Pacific and Air New Zealand on the flights from HNL to Australia and N.Z.: there's already five airlines serving those routes)
* DL already has direct flights, often multiple per day, to here from all the key cities such as ATL, DTW, MSP, SLC, PDX, SEA, LAX; and of course likely more would be brought in for connecting traffic

While there are a few disadvantages, such as:
* slightly longer total travel time to N. Asia destinations like JP and KR, due to HNL being more down south and not in the northern circle route or what not is the loop going closer north called
* a bit annoying international arrivals, with the bus'ing (but that could be likely improved upon with enough additional passenger traffic and proper walkways built to the immigration facility to avoid the busing)

all in all it would not be a bad thing and would have DL doing its patriotic duty and creating more jobs in the US vs. in Japan, while also contribute to a generally more pleasant experience to its passangers (connecting at HNL is rather nice) and provide a distinct service for connecting in a place that many passangers are also happy to layover in for a day or a few (potential extra revenues for upselling hotels/etc. for such optional layovers) and also realize savings for West Coast - HNL lack of catering and generate reveue on sold food on those flights. But, again, I realize it's just wishful thinking.