It is true and it may never go mainstream but remain localized. For example, is a Russian ruble mainstream? I wouldn't go that far. It's not a world reserve currency and you can't use it to pay for goods and services outside Russia. You can exchange it to other currencies almost anywhere in the world, but it's the same with Bitcoin. Localbitcoins traders can be found all around the world and bitcoin exchanges exist in most countries. So, we don't need Bitcoin to be mainstream, we just need it to be there. To remain as an option.