Sony's make mirrorless full-frame, they already able to replace SLRs for many photographers. It's not a trade off as you suggest, because Sony image quality is

Sony's make mirrorless full-frame, they already able to replace SLRs for many photographers. It's not a trade off as you suggest, because Sony image quality is rated as one of the best, if not the best in the full-frame market. The new "iii" series cameras have much longer battery life than before. The size of mirrorless cameras is only one benefit, and there's no particular reason that a mirrorless camera couldn't have a big Nikon D5 style battery if there was a market for it. I don't see any particular reason that mirrorless cameras won't completely replace SLRs in time, a mirror is no longer neccessary, like it was for film. No one would make a new SLR system if they were starting now, and they haven't, all the new mounts are mirrorless.