I honestly can't see London expanding much more than it is now. Cities are built on trade, and considering that London already trades with the US and the Mediterranean, trade is pretty much stagnant at this point. Unless some middle-eastern country or African country suddenly becomes civilized and a power (which I highly doubt would happen), London will likely stay the same. The only reason the east coast of the US is expanding is because of people who like urban life that move there and slowly expanding South American trade. I can, however, see the West Coast of the US and Asian cities expanding drastically over the next few years, due to the ever-increasing technology market and growing populations.