As already discussed several times on the forum, updates eventually come, but you can't expect them to appear as soon as the real life change is in place, because in order to do anything, we can't use just a chart, we need pictures, aerial screenshots, etc.
As of today, none of these are available on services like Google maps or MS Bing, you can't expect we would have them before they do, unless we set up our own aerial survey mission, which wouldn't be very good to the product price...
In this case, adding a underpass is even more complex, so I'd say it qualifies for a major update, like the JFK V2 one. At this time, the scenery designer is working on another project, so I guess we'll start discussing it after that one is released.