He... "told the Evening Standard that he hoped house prices and rents would skyrocket even further in London so he could make more money."
Can you point me to a source which quotes him verbatim as saying that as the ones you have linked to date do not appear to demonstrate that.
Secondly, what is an acceptable rate of return on an investment - or more to the point, what level should acceptable investment income be morally capped at between (i) go up quite a bit, and (ii) skyrocket, and why?