I think it's highly likely he will plea out. They are appointing him an attorney, and even if he decides to plea out and make a deal, they still have to go through the process of formally charging him, etc.
IMO, having spent 6 years working as a legal assistant - 2 of those working for a criminal defense attorney - if it walks like a duck and talks like a duck, yadda yadda. He had intimate knowledge of the crimes and he told them where everything happened. The only way an attorney could get him off at this point is if they were able to form a convincing argument that his confession was obtained under duress. But that still doesn't explain how he knew the intimate details of the crimes. MOO, IMO, JMO.
I hope they do a plea deal for life w/o parole. It would be a shame to drag WHs family through a trial. But who knows what tack this might take once an attorney is appointed to him. Hopefully they don't cook up some "diminished capacity" or some other ruse. Sometimes it's just the right thing to do to say, "yes, I did it. I accept full responsibility and the repercussions." Because this dude is dangerous and needs to stay locked up permanently.