I wonder what difference it makes who visits ? as long as we get videos of ASICs performing, and pictures of the assembling line, then that's all the proof we need.
Don't you think by then that will be a moot point? BFL will probably have videos already posted of the things running before anyone visits.
In person visitors will allow for a third-party audit of the devices' hashing speed. Videos can easily be faked if the entire setup is controlled by BFL.
I hope this visit happens sooner rather than later. It would be good for BFL as well as they are losing sales to their competitors due to a lack of transparency.