Emissions aren't the only thing you need to measure - you would also need to factor in resource consumption for manufacturing. The conjecture that the economy can continue growing on virtual goods is an interesting idea, but you can't eat virtual goods and if the economy growing also depends on population growth, something will break at some point.

Note: I'm not entirely convinced economic growth depends on population growth, but historically that has been the case in most countries that haven't exhausted their windfall natural resources like oil and have healthy export markets.