Sorry but I refuse to believe my skin could EVER be taut and firm against my body no matter how much weight training I did (although I do firmly believe in resistance exercises for toning and creating nice contours).
After three decades of being hugely stretched, the skin on my stomach will never shrink back to the way it was in my teens. For the muscle to replace fat enough to fill my stretched skin, I'd have to pump iron until I looked like Arnie in his hey day. Not happening.
I think a certain amount of shrinkage may happen but could take time after rapid weight loss so I'd probably say that whatever hadn't shrunk back a year after having lost lots of weight (even after exercising) isn't going to.
This is just my opinion of course, but gained through years of observation and experience (I lost 10st in 2006 and the skin that was hanging was just that - skin - not pockets of fat).
An interesting article all the same and I'm open to being convinced by anyone in their late 40s who has lost a large amount of weight (after decades of being obese) and who has done weigh training sufficient to shrink the skin back and consequently has NO sagging.