maybe he realises that southampton have peaked. they can only do worse. for guys like pochettino, lallana, schneiderlin and lambert, their stock might be at its peak right now, and therefore it would be a good opportunity to cash in on it.
i really wouldn't rule out southampton being in a relegation fight next season. we've seen it before. the only teams who have basically no chance of relegation in the premier league are us, man utd, liverpool, arsenal, Emirates Marketing Project and chelsea. for everyone else, relegation is a very real threat. and lambert would be wise to move on at the moment (at 32) and not risk relegation.