The last recruiting phase ran from about Oct 2005 to Aug 2008 which will give you an idea as to how many pilots will be exiting intial type freeze after 5 years. Expect bids from SH to LH until about Aug 2013!
There have been concerns within the training department as to loads on the TRI's/TRE's with the requirements to run continuity training (LPC/OPC/ATQP) alongside conversion courses and, eventually, ab-initio courses coupled with the implementation of two new fleets requiring the training of TRE's/TRI's and TSC's next year. This might cause a slowdown of release of experienced SH FO's as the maturity of the fleet starts to suffer (business terms obviously as the current maturity of the fleet shows high/stable by the SESMA profile).
There is also a strong rumour that Boeing is pushing the 748 very heavily toward BA who, as the largest single fleet operator of the 744, are one of Boeings premier customers. Boeing are citing delays to the 380 programme and training/operating difficulties as a major reason to purchase the 748. The company is, apparently (SEP forum), listening and keeping 'all options open'.
Interesting times ahead! Perhaps that oft banded about 'long time to command' could well be changing within BA as the new business plan calls for expansion and renewal!
Have fun.