>Do you think the transport system can handle increased density of upward building?

Depends if the rate of take up of cycling increases IMO. The year on year increases have been pretty consistent and don't seem to be slowing down. Sadiq putting on 'hold' (read cancelled) any new cycling infrastructure is likely to put an end to that though.

Don't forget we've got Crossrail coming later this year as well. That should take some strain off the central line in the mornings at least. Quicker Crossrail 2 get's off the ground the better though as the Northern line is a living hell in the morning. Getting on at Clapham (anywhere) and going north just is a 5 to 15 minute wait.