While the frame under the skid plate is obviously terrible, the rest of the frame, at least from the pictures, looks OK. Even the torque boxes look alright. I have to disagree with the others who say that if the skid plate area is that bad, then the frame is probably just as bad everywhere else. That really isn't the case with TJs. Thanks to the lack of drain holes, water and salt and muck collected at the lowest points of the frame without anywhere to go. The rest of the frame is *usually* OK, though obviously not always.
What you showed here is definitely fixable with Safe T Caps. The rear control arm area is probably also rotting away, so you'll most likely need the full channel caps. But you should naturally check the rest of the frame first. The other part of the frame that occasionally rots out is at the rear corners. How does the frame look there?