User blog comment:FairyRaven/Fairy Tail Chapter 437: Magnolia, Review and Commentary/@comment-24546844-20150525170715/@comment-24546844-20150525232018

Well, this timeskip showed us a bit of this. It seems Wendy hasn't entered puberty yet, even before the timeskip Hiro just used Cancer's magic to sort of retcon her haircut that as supposed to show her developmennt, no major character changed at all, and the major change in Natsu's appearence got cut by Cancer.

My guess is that Mashima just like the characters how they look now as he's acoutumed with drawing them. I won't lie I like them this way too so I do hope that Mashima doesn't try any drastic change. One of my biggest disapointments was when he changed Elfman's design, that was really nice the way it was, to the current mass of muscles that he is now.