Firstly, the arrival of the 787 and a320 is not a fleet expansion, rather it's a fleet replacement. As this is the case I wouldn't hold your breath on any extra vacancies being created during this time due to aircraft being added to the fleet (although the 2 options taken on the 787 late last year may help).
`There's a lot of aggressive work going on in that space. We'll end up with 25 wide body aircraft, a mix of 777s and 787s and that's going to enable us to deepen existing markets and access new markets'
http:// http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=11116177
With a current fleet of 20, I would say this equates to a gain of 5 aircraft....a 25% increase.