Too many unknowns to answer that question with any accuracy. But if you lose another 25 to 30 pounds in a slow sensible way while training effectively at the same time you'll almost certainly get faster.
Cyclists that train with power meters often think in terms of watts per kilogram (w/kg) as a measure of fitness. Being able to sustain more w/kg for sustained efforts as in being able to hold 2, 3, 4 or more w/kg for approximately an hour is a good way to compare capabilities and fitness between riders of differing size and weight.
Drop the weight and maintain your same fitness and w/kg rises. Increase your sustainable power and maintain your current weight and w/kg rises. Increase power with effective long term training while dropping weight in a slow and sensible manner and w/kg rises even faster.
FWIW when I returned to cycling and race training after more than a decade away from the sport I struggled to hold 220 watts for a 20 minute interval (a common weekly training interval duration and a good way to track sustainable power) and I weighed in near 200 pounds. A year later I was sustaining roughly 300 watts for my 20 minute training efforts and I'd dropped over 45 pounds. That's the difference between 2.42 w/kg and 4.28 w/kg for 20 minute efforts. My weight has gone up or down by a handful of pounds since then but with continued training my sustainable power has continued to climb as have the watts/kg which has made all the difference in terms of riding enjoyment and racing success.
In speed terms I tended to get door to door average speeds on training rides in the 18 to 19 mph range when I started training again. A year later I often managed 20-21 mph door to door speeds, granted I was living in Wyoming then with a lot of uninterrupted open roads and the speed that comes with thin higher altitude air but still the improvement was very noticable.
Bottom line, no one can tell you with any certainty how much faster you'll get through weight loss or training but you'll almost certainly get faster and feel better as long as you don't try to rush it, go to crash dieting or adopt some poorly thought out approach to training (too much, too little, none at all...)
Good luck,
-Dave
