One thing is for sure: when the Olympics come to town, so do lots of citywide improvements. Cities that are chosen to host the world's games are also majorly responsible for beefing up infrastructure to handle the influx of tourists, and that extends well beyond hotels and eateries. Things like Wi-Fi also matter these days, and it's vital to stay connected when in throngs of people. Due to that, London's famed Underground service will be equipped with Wi-Fi prior to the 2012 Games.
London actually doesn't have too many Wi-Fi hotspots (at least for those without a BT account), but that should be changing in the run-up to the Games. A trial has already been completed, and by the time the events kick off, the entire Underground should be piping out Wi-Fi to riders. A total of 120 stations around London will be outfitted by June 2012, and as we alluded to, BT customers will be the only ones who have access for free.
If you're on O2 or Vodafone, you can also connect, but there's no telling how much it will cost. Also, the Wi-Fi will only be available on the platforms, not while riding. That's a big pitfall, but hopefully it'll expand in time. There's also a good chance that these hotspots will be crammed during the Olympics, but hopefully they'll be useful right after the games wrap up.