Yes. Even the persistent memories that attach to the memory bus are currently quite a bit slower than DRAM (5-7x from estimates I've seen), while the difference with PCIe-attached ones is even more.
I'm not sure what the future holds in terms of latencies for non-volatile storage but sub-DRAM levels aren't within reach yet.
I'm not sure what the future holds in terms of latencies for non-volatile storage but sub-DRAM levels aren't within reach yet.