Personally I'm seeing about an 8-10ms reduction, so from 60-70ms to 52-60ms. I'm on a fiber connection so my speeds and latency tend to be pretty consistent to my ISP, but despite all that the servers have felt rather laggy for the last 6-12 months, especially during peak hours even if my own connection showed no noticeable difference in latency. My best guess is that the data center was previously overloaded, and the details SE have given us for part of the reason to move the data center was just that. Since my ping is apparently not changing much, I might be in a good position to get a feel for if the new data center is better capable of hosting the game and has less latency due to not being overloaded.

In other words, a ping of 10ms wouldn't mean much if the server was overloaded and took 200ms just to process the input, so if the cause of lag for most people was related to server overloading, they might notice improved gameplay even with increased ping times.