The rail linked terminal was part of the Schiphol 2000 plan drawn up in the early 1990’s. The original plan was to only have a remote pier on the other side of the motorway connected to the main building (T3) by means of an unmanned raillink.
The plans of Schiphol investing € 1 Billion in new piers and passenger facilities are part of an apparent agreement reached between Schiphol and KLM in late May 2013. This was widely reported in newsbulletins and newspapers in the Netherlands. Just Google it.
The plans for a 7th runway do exist, but a decision has been postponed until 2016. A delay from the earlier plans to build this runway in 2015.
The newspaper article you find under this URL will give you an idea of where it is planned. The land needed for this has already been earmarked so building can go ahead one the plans have been approved and all legal procedures have finished. The new runway is dubbed “Tweede Kaagbaan”.
So far most plans Schiphol have presented in the past have been successfully realised. Yes, it takes quite a long time, but the result is a world class airport that is appreciated by many travellers. I’m sure they will pull this off as well.
What the Dutch did and do at Schiphol is envied by a lot of people and companies in the London area.