31, no children, ongoing weight loss via strength training, stubborn panniculus remains. Will I need panniculectomy? (Photo)

Glad to hear your active lifestyle is achieving weight loss and improving the quality of your life!  Unfortunately, as every mother and every bariatric patient will attest, your skin doesn't always want to cooperate with weight loss, and excess skin is unresponsive to diet and exercise.  When you have achieved your desired weight and fitness goals, consider a formal consultation with a Board Certified Plastic Surgeon to discuss your options.  As young as you are, and having achieved weight loss, you may have certain aesthetic goals for your body and your torso.  A consult will determine if your goals will best be met by a panniculectomy, abdominoplasty, extended abdominoplasty, or even body lift.  Congratulations on what you have already achieved, and best of luck!

Congratulations on your weightloss!
Following achievement of a stable goal weight, an abdominoplasty (saves and repositions the belly button, tightens the abdominal wall/diastasis recti) would be a good option. A panniculectomy amputates the belly button and removes excess skin hanging to the pubis/knees; I think you would appreciate a better result with an abdominoplasty.
For either procedure, weightloss reduces intraabdominal fat, which is not addressed by this procedure or liposuction.  Reaching a stable goal weight is key.