Always a good time to buy SSD.
Mechanical media needs to be put to death once and for all.
SSDs are already choked by SATA 6G, and I don't see SATA 12G around the corner any time soon. Other than tiny incremental leap frogs in IOPS that serve more as marketing pissing contests between vendors, I don't see current gen drives being surpassed in performance any time soon outside "exotic" measures like PCIe cards.
Unless Thunderbolt takes off and replaces both USB and SATA, we are probably stuck at SATA 6G being the bottleneck for a single drive for quite some time. The only thing that will really happen any time soon is prices coming down and capacities going up (but aren't we used to that in this industry?). But then you just say "dollar cost averaging" and you buy more SSDs in higher capacities when that happens. 😀