I am on the fence when it comes to changing handling lines. While I know most vehicle speeds at this current moment are not the most realistic because, as you pointed out, vehicles top out ~140-150 even with most super cars. I believe that making ever thing faster is going to cause extensive loss of fun due to the inability of most to be able to control their vehicles.
From a development side of this, this would take probably if not close to 4-5 months to get this fine tuned and perfect as we would have to review each vehicle in the game, find its IRL counterpart and try and tweak it to fit as close as we can. I know there are already resources out there that do this to an extent with the default GTA vehicles but we would have to then do it for the addon vehicles and police fleet.
At the end of the day I will go with what the community wants, but I just do not want to spend the time and work and then roll back because they arent liking what they wanted.