I don't see how extending it to the mouth of the river is going to make things safer. According to the link, "The petitioners are requesting this action based on their belief that such a restriction is necessary to promote safety within the waterway." From what I've heard, this is coming from Bowley's and if so, I think they just want to reduce the wake action that attacks them every now and then, not to promote safety in the Middle River.
I'm all the way up at Cutter Marine Yacht Basin and it's already a 20 minute ride through to the current no wake markers. Moving them all the way to the mouth (I'm assuming their looking at the location being somewhere around the red marker by Bowley's) will add another 20 minutes or so. That'll mean almost 3/4 of an hour for me to get through the no wake zone. The folks up Frog Mortor Creek will have even a longer ride.
I'm all for promoting safety, but in my opinion, this is just a ploy to benefit the owner's of the slips at Bowley's, which is a very small fraction of the boaters who use Middle River, and won't make much of a difference in safety.