Not so to the Japanese at least. To them, almost any even number does not spell good luck. Generally, it's any odd number like 1, 3, 5 and 7 and so on that they believe is good luck. To actually bring a gift to a Japanese in sets of 2 or 4 items, for example, will offend them and could set things off on the wrong foot!
Frankly, it's crazy for the A3XX would be called the A380. It's just not common sense. There isn't such a thing as an A360 or A370 built or even designed yet! If it was called the A380, then a future "A360/370" family, whatever the a/c will look like, might not sell nearly as well, for customers, especially those in Asia might view the "A360/370" as inferior products!
If this sounds nuts, look at how McDonnell Douglas had to change the designation DC-10-20 to the DC-10-40 because the DC-10-30 was already built. JAL and Northwest wouldn't buy this aircraft unless McDonnell Douglas changed the designation. You have to think about the first impressions any manufacturers have make on any product they sell such as cars and food products. Airlines and commercial aircraft are no different.
So it's most likely to be called the A350. BTW, the A3XX was once referred to as the A2000 in the past, when Airbus was just getting started on designing the A3XX.
The A330/340 was never called the A3XX in the initial design phase. The A330 was actually referred to as the TA-11 and the A340 the TA-12 when they were first designed in the 1980s.