if there was going to be an extension it would be at the Dinnington end.
That is what I have heard. But this is where airport managers show their lack of understanding about airliners and their operation. After all, most of them are little more than shopping mall landlords and parking concession operators. But returning to the problem. On runway 25, most aircraft at NCL are restricted on the second segment climb. This is because of the higher ground within the splay around the extended centreline of that runway. The splay is considered by measurement from the end of the runway (well TODA actually). So you could well find that no matter what length of runway is built, the weight that can be lifted by an aircraft won't increase by much at all.
PM