I caution that report as the its the same reference point the BA Source references the enthusiast site Jethro !
That said it is known that the existing 737-400 models are to leave by end of W2014/15 season and that they are to be replaced with 32x frames on a one for one basis.
We also know that BA already has ten A320s on order for delivery in 2014 anyhow.
Until is see anything official I believe these are the same frames with just a rolling order of 6 extra in Q1 of 2015.
I am sceptical that just a few days after the release of a five year plan a further big and unacknowledged extra investment programme could be sanctioned.