No, I haven't seen him this year. I've seen reports here and apparently he is still getting walked, though maybe less often.
There are several aspects to 'quickness'. There is reaction time, foot speed, first step acceleration, etc. It is not enough for a player, any player not just Stanley, to be fast 'for his size'. He has to have speed/quickness that keeps up with the other players. He has to have the speed to be able to maintain good gaps. I think he has always had adequate top speed but it takes him a while to get to it. It takes a while to change the direction of that big body too.
Everything I see here, from those who have watched him this year indicates that he still lacks overall quickness, though he is getting better. The NHL game keeps getting faster and emphasizing skill over brawn. A big pylon who occasionally scores is of no use to us. If he can learn to defend against the high speed, high skill forwards who are dominating the NHL, I don't care how he does it. But if he can't do that, I don't care that he is BIG Logan Stanley.
He may never be fast enough, or quick enough if you prefer that word. But if he can learn to anticipate the play and be effective by being in the right place at the right time its all good. I think that is what Chara has managed to do to a large extent.
To date there is nothing in his resume to indicate that he is likely to have a strong NHL career. But he is having a decent AHL rookie season. He is improving. If he can continue to improve he might be good in the future. At some point the improvement will stop. We know that for certain. We don't know when that will be or how good he will become before that happens. But right now he is not leading of the pack of those who will make it.