Some technical stuff for you
I wrote about this functionality a few weeks ago, and it appears no solution is in sight. I have been given a bit of information as to why it may be difficult to address.
For some of us shooting the 5D Mark III, there is an issue that is driving some, not all, photographers bonkers. That is, when shooting in AI Servo mode, the focus point we have selected does not illuminate red, like it does on the EOS-1's like the 1D Mark IV. The 7D has always had the black focus points in AI Servo and we never really heard many complaints about it. However, since the 5D3 came about, there have been countless complaints about shooting in AI servo mode without the illuminating focus points.
I finally spent a serious amount of time with the 5D Mark III, and I am on the side of it being extremely annoying that I can't see my AF point in AI servo mode in various situations. Lowlight, black shirts, birds in flight and that sort of thing. With the 61 AF points, I do move the focus point off of center during AI Servo usage.
As mentioned, there have been lots of forum threads on the topic and I have finally heard from a few people what the issue is.
Below is some technical information about why (correct me if we're wrong).
The transmissive LCD is the issue with both the 5D Mark III and the 1D X. Despite greatly improved AF, the exposure is affected by the red light of the AF point. This is why they do not light up in AI servo just prior to the exposure reading being made.
In order to solve the problem, Canon will have to figure a way to turn them on (red), yet adjust for the exposure differential. That isn't as easy as it sounds, as each focus point will affect exposure slightly differently not to mention it's also dependant on which exposure mode is active.
Can it happen?
It's possible, because I'm told Canon is working on a solution. They do know a segment of photographer is having trouble with the black AF points. I am told the 1D X will launch with the same functionality as the 5D Mark III.
For some photographers, this is not an issue, or even a minor annoyance.