[Maritime Q-Scout]

I would think someone like Big Time could answer this better than I, however I would assume it's to give more clearance for the heavies

While the current runway is sufficient, a longer runway would probably make landing easier (wouldn't have to touchdown as early) and takeoff easier as well (don't some planes eat up the entire runway on a hot summer's day? A few extra hundred feet would be nice).

But perhaps the answer is simply, to provide easier access for the A380, or new generation 747's (not necessarily as a main visitor but as an alternate?)

Of course this is all speculation on my behalf.