Earlier this year Sustrans was given £200,000 to research the proposal in detail but I have not heard of the output from this research project having been published, and without seeing precisely what is being proposed it is a bit difficult to form any sort of opinion about the viability, the logistics and the impacts.
There's a story about it today on The Guardian website: http://www.theguardian.com/artanddesign/2015/nov/24/revealed-the-new-thames-bridge-proposal-thats-a-no-brainer
When anyone hears anything new about the bridge I'd be grateful for any updates. My email address is in the header at the top of the blog if you would like to get in touch.
The Brunel Bridge website is at: http://brunelbridge.london/.