About 6 months after I joined a mate asked if he should accept a 320 course or hold out for the Jumbo....3 months later they turned off the tap. Fortunately for him he took my (limited) advice based purely on the mantra that seniority is everything (in BA at least).
There are mutterings of LH recruitment - but remember that, when the likes of me are unfrozen and get to move, we'll still be above you in terms of seniority, so you'll still get everyone else's leftovers. That's not meant to sound derogatory but a simple fact of BA life (from someone who has been 50 off the bottom of the company the past 3 years!)
If a move to BA is right for you, do it as soon as you are able; given your demographic, you are unlikely (as am I) to see the LHS of a LH aircraft anyway!!!