How do you mean the other way? As in NYC? If so then I definitely agree, I really cannot see why it couldn't work (except from US airlines having high cost bases and not really offering the service you pay for as a result, or so many say).
I haven't seen it in person but how AKL handles the 3 A380's at once is really impressive, all arriving and departing at the same time. AKL doesn't have that many passengers, hence they all go via SYD, BNE and MEL. I'm not even sure there would be a market for DXB-AKL-DXB, especially not with the flights they have currently.
Anyway... In terms of NCL, I think within the next 2/3 years EK will do something at NCL and I would say that will probably come as either x10/x11 weekly, possibly on A340 500 or 777 200/200ER equipment... Maybe (but please God I hope not) on the A330's. Suppose a slack 77L could work too.
Regarding EDI, I would hope the following will be their logic:
2015/2016 - Get GLA up to A380
2015/2016 - Increase NCL to 10/11 weekly and introduce first class
2017/2018 - NCL 2 daily, GLA 3 daily, then start EDI after securing their existing markets
I'd say 4th daily MAN, daily STN, a South West service, another daily rotation to an existing London airport or two and maybe 3 daily BHX will all come before or around the time of EDI. Then they may start exploring options for new UK markets but I don't know where could be left without starting to cannibalise...
But I've gone a bit off topic... The longer places like Canada, Germany, China, France and India (although they are pretty lenient really) keep restricting flights and blocking markets under the façade they are supporting their local airlines, the more other markets such as the UK and USA will thrive on more opportunities given to them.