SSDs don't have to reach price parity with hard drives to displace them. They just have to be the best decision for someone building a new computer. For most users, it's better to redirect some of the dollars you could spend on a giant CPU towards an SSD because that will actually make a difference to performance. In the same way, if you are building a gaming box, you want to buy a reasonable graphics card, rather than a giant CPU and a crummy one. (Personally, I don't play games so much any more, but I know some people who do.)
There was a time when graphics accelerators were unheard-of and everyone just used onboard video. But graphics accelerators didn't have to reach price parity with onboard video to win. They just had to become the best choice for most users. (Nowadays, onboard video is making a comeback due to some excellent chipsets from Intel, but that's another story...)
To sum up: in laptops, phones, music players, and tablets, hard drives are either entirely phased out or nearly there. HDDs will be with us for a while on desktops and servers, but mostly as the new tape drive.
I wonder what kind of performance Tux3 will get on SSD. SSDs do benefit from larger contiugous writes as opposed to small, scattered writes. So to the extent Tux3 can provide that with its deferred I/O mechanism, SSDs will benefit. Of course, SSD firmwares also try to accomplish the same general goal of write coalescing. So there is a risk of burning CPU on something that firmware is already doing.