While search engine trends aren't reality, they're a reliable indicator of what interests people in real life that they research on the internet. Again, headlines don't match reality; look at the following chart, and see that as media mentions black metal more and mainstreams it, it fades out from searches, which means that fewer people need to see it -- they're inundated in it and disinterested. Read More >> Has Metal Jumped the Shark? Cool analysis of charts and net statistics. It shows how accepted metal has become, and at the same time, how people are losing interest in searching for it. I guess what was once scary is now mundane. Will that make it lose its audience?
I think this will mostly be at the expense of the more commercial bands in the genre because metal (and perhaps black metal most of all the subgenres) means a lot more to a lot of people than a nice trend or a way to piss off the parents. Who cares about numbers anyway, in previous decades there were much less people into metal and it didn't disappear then, either. Something that you do see, lately, is an upsurge in other genres of music that offer the same mood and emotions as certain styles of metal do, like martial industrial, "post-rock" (I hate that term), noise, drone etcetera. This may be a factor in this decline of searches for metal. Still I don't see a reason to worry. I wouldn't stop listening to metal no matter how few others do, and I'm sure the same goes for you and plenty of other people.