How much faster will I be if I lose 10kg (from 100kg, all else equal) All else being equal (power output, weather, wind resistance, etc.), how much faster will I be if I lose 10kg (going from 100kg to 90kg) while riding? 

Acceleration and climbing might be much different, but while riding steadily on a flatish road outputting the same power as before, how will my cruising speed change ?
According to BikeCalculator, assuming you drop 10 kg while everything else remains the same (power output, etc.), you would travel 0.3 km/hr faster over a 50 km ride, on the average. In other words, at 100 kg, assuming an average power output of 150 Watts, you'd average 27.54 km/hr over a 50km ride if you weighed 100 kg; doing the same ride at the same 150 Watt average output, you'd average 27.84 km/hr if you weighed 90 kg. That's an increase of very slightly over 1% in speed. 

Having just gone from 100 kg to just under 90 kg over the past couple of months, however, I'd say that BikeCalculator understates the practical impact of losing that kind of weight. Since climbing, in particular, is basically all about the power to weight ratio, I have certainly noticed how climbing has gotten easier and how I can go faster up various climbs, and I intend to drop another 9-10 kg. For example, if you ride on a mix of terrain, both flat and climbing, you will gain more than 1% in average speed. Assuming the same average power as above, here is how average speed will increase with a 10 kg weight loss for climbs of different slope. 



Best of luck dropping the weight and keeping it off.