I almost posted the same question the other day about the High-Speed 2 rail line. Answer in both cases from me is that I don't know, time will tell.
Those in favour of the Olympics, (being publicly funded), say that it leads to long term benefits such as jobs, etc, long after the event....but I've seen several reports lately that say that has never been the case in the past, often the sites just end up as "big white elephants" so I suppose time will tell......(and even then, the financial benefits will be London based).