Considering the speculation I have a hunch now itll be Germany. London is too expensive (and will get up to 20% more so over the next few years because of enforced wage rises). Even UK outside of London would get too expensive.
Germany on the other hand have many large companies able to offer the infrastructure at lower cost because of competition and readily available resources. The ping will better suit everyone too.
Still, cant always take the logical approach in guessing what SE plans are... could end up Russia :P