The opposite is true... speed them up and have more of them. We have enough slow courts these days. There is no more S&V on hard. At least keep it alive (or "bring it back to life") on grass.
Speeding up the grass won't spark a renaissance in SV unless the hardcourts are correspondingly sped up - to make it worthwhile for kids and juniors coming up to adopt a serve-volley style and get success with it for more than just 1 month of the year. All that will happen if only the grass is sped up or the balls made lighter is that you'll just get big servers dominating again, whether they come to net behind it or not.