More likely, mirrorless will be dead in 5 years as their consumer portable market appeal is totally eclipsed by the even higher quality successors of cameraphones like the Lumia 1020.
Meanwhile, the pros who won't accept quality/functionality loss for smaller size - something all mirrorless including the A7 suffer from - will continue to use DSLR. We all heard this same dire prediction when mirrorless first came out, now we are hearing it again with mirrorless full frame out - which btw has no size advantage like crop mirrorless due to the lenses being much too large for the tiny body. In fact I am not sure what mirrorless full frame brings to the table except novelty - "look how tiny my camera is without a lens!" then put on a zoom lens and it becomes a pain to handle.
If you don't believe me, simply look at the sales trends, mirrorless is selling poorly and suffering worse than DSLR.