The newer SSD's promote a form of sequential writing (ring buffer?) so that writing a file to the disk is not always done to the same location. This helps extend the limited read/write of the disk (but at 10K R/W will we reach it?).
We run into serious issues when using a OS like windows which uses a swap file and continually updates the disk. In cases like this, it's best to have a magnetic drive as a secondary to absorb the constant read/writes. However, this defeats the purpose of using a fast SSD in the first place.
I think both flash based storage (SSD, etc.) and disk drives will continue to have a place in the market for the foreseeable future.
There are two things that concern me about flash storage.
1) Not knowing when flash storage locations are being used up/retired due to the limited number of write/erase cycles (on a disk drive you can read the defect lists to get the locations and count of defects).
2) The difficulty verifying that data is erased from flash media (see paper from UCSD http://www.usenix.org/events/fast11/tech/full_papers/Wei.pdf).
I think that the second item will become a very serious issue for business, government and individuals as more and more devices use flash based storage (think tablet computing as well as smart phones).
It was announced this morning that Seagate is buying Samsung's HDD business for $1.4B.
At least Seagate and WDC will continue to make hard drives for the foreseeable future. Some of us are now accustomed to having multiple terabytes for photos, videos, backups, etc., and it will be a very long time before I contemplate buying multiple terabytes of flash!
SSD is not as reliable as HDD when you look beyond 2 or 3 years. SSD has lower capacity. SSD has a significant price premium over a HDD. SSD performance is not high enough yet to justify the cost increase over a HDD for most consumers and this is unlikely to change in the near future. SSD does have a future, but it is maybe 10 to 25% of the data storage market a decade from now. Most people who buy an SSD will also buy a HDD.
Either Seagate or WD could buy Samsung's business. It is not clear why Samsung would need to sell the business since Samsung has excellent cash flow. But companies do things for a variety of reasons. Multiple companies these days are involved in SSD. Only a few are capable of designing and building HDD.