The United Kingdom probably won't become as big as Japan largely due to the handheld race. Japan has outsold the UK 27m to 6.5m.
However, in the console race, I do think that the United Kingdom can slowly get close to Japan, but that's still years away.
Currently in the next-gen hardware race, it's Japan's 5.6m consoles to UK's 3.5m. Definately not close, but closer than the handhelds.
However, mainland Europe, I believe, is where it's at. There's a huge population base (about 350m) that have relatively decent incomes that aren't buying a bevy of hardware.
For next-gen hardware, you have:
United States: 15.2m Consoles
Japan: 5.6m Consoles
UK: 3.5m Consoles
France: 1.85m Consoles
Canada: 1.6m Consoles
Germany: 0.9m Consoles
Spain: 0.9m Consoles
Italy: 0.65m Consoles
Scandanavia: 0.6m Consoles
Other Europe: 0.75m Consoles
Austrailia: 0.55m Consoles
South Korea: 0.3m Consoles (est)
Taiwan: 0.2m Consoles
So in the future, UK as well as some European markets could become huge.
Back from the dead, I'm afraid.
