To the question in the topic: Yes, i think mechanical storage (harddiscs) have a future. Flash does have a nice track of groth in space per $, better then harddrives have. Stipulating into infinity flash will pass harddrives in GB/$ sometime in the future, but things will of course not have the sema growthrate into infinity. Sometime both technologies will stop. Just like the clockspeed on CPU's that everybody belived to grow into infinity at the same growthrate as always, just a few years ago.
So, how far will flash and harddrives keep the same growthrate as today? I dont know. But my guess is maby 5-15 years. That also means that when 0,85" and 1" harddrives meet hard competition by flash today, altso 1,8" drives will meet that competition in a few years. If 2,5" drives will meet the competition or not before growth slows down and maby stops, i dont know, but i'm convinced 3,5" drives will remain untoched.
Another trend is that OS and programs dont increase in size as fast as other storage needs. That may split the market in a flashmarket for OS and programs, and a harddrivemarket for general storage.
Write and read-speeds on flash is actually a far smaller problem then many thinks. Its pretty easy to RAID its way out of htat problem. The Raid-controller even dont have to be on the motherboard. It can easily be integrated into a part of a SSD-drive, and thus offer very fast transfer rates compared to harddrives. (Not only the more expensive OneNAND, but altso simple and cheap NAND)