Ok. Ta.
The thing that is missing here is that with the ICAO Flight Plan changes, all the systems have to be changed to cater for the new requirements in a specific order and short time frame.
Given that making >1 significant change (and this includes data set changes as well) at a time is a considerable risk (read up about the skyguide disaster) then there are very limited opportunities to reschedule a change.
For example, there is a significant change to the AFTN switch going on tonight and nothing else. The longer NIS took to get out there, the less time the Flight Plan 2012 changes will be on the external test bed and that in turn has its impacts.
There is lots of pieces to the puzzle that are waaaaay beyond the view of external users.