They had plans but I don't think it worked out the way they thought.

"Andy Higginbotham, director of sales and marketing for Samsung's Hard Disk Drive Group, notes that NAND flash's cost per gigabyte is expected to decrease by about 50 percent per year. Considering that timeline, Higginbotham says, we can expect to see hybrid hard drives incorporate 512MB of flash in 2008, 1GB of flash in 2009, and 2GB in 2010--all for the same cost as integrating 256MB today."

It might still happen but I have doubts.
I'd say, HDD's for storage and SSD's for speed , there may be a market in between.

It's a great idea though, this way notebooks/small laptops and low-mid end computers could have the "best of both worlds".