Leaving aside the fact that, for me anyway, "Too soon isn't soon enough", the only new build steam locomotive that I know of that has been given a very specific timetable for completion is 45551, the Unknown Warrior, for the obvious reason that it must be ready (in steam and all systems go) for the Centenary of the Armistice in 2018. It is planned (according to the Group's website) to have the loco finished for testing in 2017. As a member of the Group, I receive all the newsletters et al and I've no reason to believe that 45551 won't make that very important date as long as, you've guessed it, the money keeps coming in.
The next new-build to steam will probably be 2999, which has been "on the go" for quite a while. The NER/LNER 0-4-4T isn't far off either whilst 82045 is coming on in leaps and bounds, as is 6880 Betton Grange.