The 'official line' is that
NR» are definitely bringing the international platforms 21 - 24 back into use from December 2011, so that the 10 car suburban trains work at Waterloo can be undertaken efficiently. So the Libdems can probably walk back on their campaign.
Source: Sept 3rd
ORR» letter to Network Rail, regarding the June update to the
CP4▸ enhancement programme.
http://www.rail-reg.gov.uk/upload/pdf/enh-cp4dp-030909.pdf This is only a net increase of three platforms, because the current P1 and P2 are to be abandoned, as they cannot be extended, and the whole layout in teh station throat will be altered so all normal operations will move 'two platforms to the right' (looked at from the concourse). P20, the platform in the international terminal on the other side of P19, is basically usable now, but they don't need it with the current timetable.
The Wolmar article in the recent Rail magazine that some members might have read, appears to be already overtaken by events, the latest Modern Railways reports the Dec 2011 date.
Running the main lines into the international platforms via a new flyover east of Clapham Junction is a long term option, mentioned in the Arup report into the WIT re-use a few years ago now, especially regarding 15 x 23m trains, but there is no date for this currently.
Paul