Wear leveling doesn't help with static data as much, or if the SSD doesn't have power. The second you stop flowing electricity through it, the degradation starts (albeit very slowly). At the rate they are going, the hard drive manufacturers should have nothing to worry about. Sure, cheaper cost per Gig will make hard drives less attractive for a primary OS, but on the other hand, HDD's can retain data while it is off for months or years at a time.
As someone who uses USB HDD's for backups (not powered up much) this is important. Some may think this is silly, but imagine if you were told you had to spin up every one of your DVD-R's every few months to keep the data intact?
This is why all my SSD's are older. Most are 34nm, some 25nm. Nothing smaller. The speed trade-off from 22nm, 20nm, 19nm and below is barely incremental in daily usage.