This electrification programme radically affects the requirements for rolling stock over the next decade. There will be far less need for diesel trains and a greater requirement for electric trains. In particular, the previously-planned procurement by the Government of new diesel trains has now been superseded. We will accordingly publish a new rolling stock plan in the autumn, taking account of the changed circumstances.
This suggests that the new build stock for Cardiff-Pompey will never happen. Expect to see cascaded Class 165/166 some time around 2016. Or maybe 5 car HSTs▸ (High Speed Train) when they start to be offloaded from London-Cardiff.