It's not so much a question of how hot the bulb or element is but what is done with the heat. For example, I've been experimenting with a 30 watt LED and mounted it on a really large heat sink like this:
Attachment 8794
Needless to say, this bulb will run cool for hours. In the same way, the bulb from HID Auto Vision claims that aviation quality aluminum die-casting is used in the casing, and integrated forced air cooling keeps the bulb cool and efficient. That's another reason for trying this particular LED. Again, all the information I see on this is positive but I don't want to make an early call that it's THE ANSWER.