By the autumn, when the excrement has hit the air conditioning (once again) in the shambles that is the "euro crisis" the Olympics will be but a dim and distant memory. So entrenched will Europe (including the UK) be,bogged down by fiscal and financial difficulties and the potential uncontrolled break up of the single currency,that any "legacy" left by the games will be completely lost in the noise.
As far as getting youngsters to participate in sport goes, only privately educated children will get much of a chance to do that at school. The teaching unions that control the State education system will not countenence anything that remotely resembles organised competitive sport and their members will not take part in any extra-curricular activities that are so necessary for that to be successful. Furthermore, most children simply do not have the application or concentration necessary to take part. Of course there will still be the few that do succeed, but they will do so in spite of the State education system, not because of it.
The legacy of the "hardware" will be a stadium that will have to be virtually demolished to make it suitable for Premiership football (the only sport with the funds to use it), a big mud hole in Greenwich Park where the horses have trod, an acquatic centre festering for lack of funds to run it, and the demolition of the fine exhibition centre at Earls Court to make way for housing. The only venue that might have a decent future is the velodrome. The Olympic Village is to be converted into predominantly "affordable" housing, which means it will be occupied mainly by foreigners and single mothers.
London has had its party but, like all the other Olympic cities in recent times, all it will have to show for its efforts (and its taxpayers' cash) is a few delapidated structures which visitors will gaze upon fondly as they slowly decay. Of course the proposed "legacy" is being hyped just as the Games draw to a close but in time people will realise that it cost them £9bn, which they didn't have, for a fortnight's street party which made them feel good at the time.