As the organisers of the weekend closures I'd like to say thank you for this post, and we would also encourage everyone who has an opinion (good or bad!) to give your feedback on the road closure. The more views we get, the better we can shape the plans for the future.
I would say that it's highly unlikely that we will ever close the road completely, as the logistics during the working week would be enormous and have a negative impact on many businesses and residents. We would however very much like to continue the weekend closures from next spring, and we are already working on a more permanent barrier solution (think rising bollards across each junction). The biggest issue however is cost (isn't it always!!) - by the time we have rented the barriers and seventy street signs, paid for the stewards, the extra rubbish collections, parking suspensions etc, the weekend closure costs around £15k per weekend, so that would need to be found from somewhere.
You mention a petition in your post, but I am unaware of this, could you please post a link to it?