Sounds like the most expensive context switch ever.
Anyway, I fail to see the point of this discussion, TFA states that MRAM attains speed comparable to that of the DRAM, which is much slower than CPU cache (at least one or two orders of magnitude slower), so that won't go away just now.
Also, the article speaks of "write speeds" (whatever that means) of tenth of nanoseconds but says nothing of latency. I suppose there are no refresh periods, which might improve over DRAM a little. It all seems very vague so far, I'm looking forward for some more technical and all-encompassing performance numbers.