Can we say that his work has been done or is still a work in progress .
It's both. Satoshi successfully released and launched the Bitcoin protocol, and it
is a peer-to-peer electronic cash, it's just not a widely used one, but it doesn't make it any less decentralized or electronic. Of course there will be always work to do, just like with any other complex software, so in some sense Bitcoin will never be finished, but that's a good thing, because it means that Bitcoin is progressing and adapting.
Some people would say that Bitcoin can only succeed if it's adopted by a lot of people, but I don't agree with that, as long as there's at least some users, then Bitcoin is not useless.
Exactly as long as bitcoin keeps being used by someone around the world then it has an use even if it is a limited one, however it is obvious we are expecting that bitcoin does in fact becomes used all over the world by a great number of people because as we know that not only means that we have a freedom when it comes to our money that we did not had since people used physical gold on their transactions, but this will mean also that the price of bitcoin will have to skyrocket because as we know the amount of bitcoin we have at our disposal is limited and that is never going to change.