I think after 10 years, year 2015, HDDs will still be around. But they will have reached their density limit. I guess a 3.5inch drive will pack about 10TB - 500TB data. The cost will be around $20 - $100. On the other hand, FLASH will still be more expensive than HDD although by not that big a margin as today. I think HDDs may disappear altogether after about 20 years.
other techniques are under development right now, like FRAM, MRAM or phase change. I think the development of these and whether they will make it to the market will mainly determine if the HD or flash will survive.