I doubt the bulb failed due to overheating. I've experimented with the LED bulb that brianinc-ville was using and its thermal management seems to be adequate - hits about 75°C and reaches steady state, and that's without the benefit of airflow while riding. Well below the typical maximum junction temperature of an LED. The bulb is also designed not to take more current than it can handle.

brianinc-ville, did you run it straight from the dynamo or did you rectify the output first? Un-rectified, I wouldn't be surprised that it got fried from being reverse biased half the time.

I forgot to mention that the main barrier to the upgrade would be the optics. Incandescent bulbs and LEDs need different optics and generally aren't compatible with each other's optics. A LED might throw out more total lumens, but it is not well focused with optics designed for incandescent bulbs.