In my opinion it should be amazing and will keep CPU mining very competative in the future.
If MRAM really replaces DRAM or this 'd leed to a total new technology it will be used on both, CPU and GPU. The nice properties of YACs hash algorithm make it very stable against technological advance. Most other hash algorithms will be performed by ASICs or FPGA in the future when they become even too simple tasks for GPU. (far future)
The only way I see YAC to loose the homemining ability requires an extreme technological breakthrue and extreme high prices. Since the calculations for its mining are quiet similiar to standard computing even then it's unlikely to become impossible on standard home hardware like bitcoin will in a few month.