and how long will it be till the next huge security hole is found?
Probably aroudn the same time as it takes for the next hige security hole in some other OS is found. The difference is the value in exploiting it.
If Windows weren't used by so many people, there would ,most likely have been no exploits for this particular vulnerability. There have been multiple vulnerabilities that have affected linux/unix/bsd that are pretty much exactly the same as this one (view image == code executes), and they were never exploited. If you think they weren't explited because they couldn't be, you're living in a fastasy world.
One of Windows weaknesses is it's large marketshare. It's a big target and there is high value in exploiting a Windows vulnerability.