Yes, if the light output changes due to engine speed I'd expect it to get brighter when revving and dimmer at idle, indicating the battery's partially charged and the alternator's doing it's job. What you describe sounds more like the alternators not got any output and it's running the bike from the battery only. It can be an optical illusion so buy yourself a cheap multimeter/voltmeter (if you don't already have one) and check the battery both at rest and under load. It should sit at about 13.2V at rest and at idle, and 13.8-14.2V while revving. If you do have a problem get it to the dealer ASAP before the battery dies.
Matt
