It could improve a good amount (20-30%) depending on what game it is.
Latency is the combined time to "put the packet on the wire" and the "transit time or how long that packet takes to reach the destination"
If your latency is 25% serialization delay and 75% transit time take this example.
100 ms one way = 25 ms serial, 75 ms transit.
Move to 5x speed service, same packet...
5 ms serial, 75 ms transit = 80 ms or a 20% improvement.
This doesn't make much difference once you get past 1 Mbs speeds but since you have very low speeds it may be quite a differerent experience.
Im my experience from traffic shaping games most will use 128 - 192 Kbs of bandwidth.