Required Navigation Performance
Tom,
You seem to regard RNP as a single aircraft system, ie a box which is bolted to the aircraft somewhere which provides 'RNP'. In reality however RNP is a concept, a state of mind if you like, more than anything else.
RNP specifies how accurate the navigation solution has to be at a given time.
The article you linked to says that aircraft manufacturers are working towards RNP certification of 0.1 or 0.15 in the future. 0.1 nm is about 180 metres, a standard runway is 45 metres wide. RNP certification of 0.1nm will not provide a navigation solution which I would want to rely on to perform an auto-land.