Just because you have liposuction doesn't mean you'll need a tummy tuck. Liposuction alone can take care of excess fat tissue, but loose skin and stretch marks must be addressed by one of three techniques: dermatolipectomy, mini-tummy tuck, or full tummy tuck. Your plastic surgeon will know which procedure, or combination of procedures, will give you the results you're after.
Laser assisted liposuction might tighten the skin a little. However, if the amount of excess skin significant, only excision will give you a good result. Unfortunately there will be a scar across the lower abdomen. You'll have to decide if it's acceptable or not.