S'pose I should pitch in on this conversation.
Tesla brings up some very solid points, and I agree with him.
Lego have gone on record pronouncing Lewa in a multitude of different ways.
Loo-wa, Lay-wa, Lee-wa. Tomato, tomahto
The name originates from the maori language, it makes sense that the proper pronunciation be based on it.
Take for instance, my name; Bill.
Bill, a name derived from the english language, only has one pronunciation. However, it is my name, and come to think of it, I want it to be pronounced a few other ways.
I want my name to be "Beel", even though it's still written "Bill".
So is it Beel, or Bill?
Well, as my name originates from the english language, the proper pronunciation would be "Bill", no fancy literation.
Regardless of how LEGO has been pronouncing it in G2 recently, you can't definitively say it's pronounced one way over the other. Simply because something hasn't been said yet, doesn't mean it has been negated. All current pronunciations of "Lewa" have come from one source, and one medium: the online animations, which are all done by the same voice-actor. We've yet to receive any alternative pronunciations, or the same one for that matter, from other sources (i.e audio books, video games, and the likes).
You can't definitively say that one pronunciation is THE pronunciation unless it makes sense from a technical stand-point, or LEGO outright says so.
Lay-wa makes sense from a technical stand-point.
It is how the name is to be pronounced in the language it originated from.
Ergo, it's a very reasonable argument to make that "Lewa" is pronounced "Ley-wa".