I'm kinda on the same page as you
@MKC .
Theoretically it could be worse but at least it's a breath of fresh air which I feel is needed.
I think they will change to Unreal 4 this year because I believe it was at the launch of PES 2018 they talked about a three year cycle, which would have come to an end with 2020. Of course, they didn't really explain what the cycle was about, but either way it's the end of some sort of strategic development process, which leaves a window open for a new one that could be implementation of a new engine (that they already worked on for mobile). Then they could move on to Unreal 5 a couple of years later.
Besides that, PES 2014 was on a new engine at the time as the last game of the PS3 generation, so if they decide to implement a new engine similarly PES 2021 would be the game to introduce a new engine as the last PES of the PS4 generation (I actually thought about getting PES 2014 the other day after seeing TTB playing it on Youtube, only to find out that it wasn't released on PS4 - I don't have a PS3).
My hope for a new engine is that it will sharpen/freshen up the game play. I feel like PES is very inconsistant; sometimes it plays great and very life like, other times it's sluggish and unrealistic (passing for example). I hope they can make it more consistanly playing good because there are real gems that pop up once in a while in terms of animations, dribbles, shots, passes, random deflections, physical battles (I could really make a great highlights reel out of this), but often I feel it's a real struggle to control both my defenders and attackers to dribble, tackle and position themselves, and every now and then I get matches where it feels like everything is just out of my control.
If they could start by making it more consistant they'd really come a long way gameplay wise, but it's still a major task to improve the game overall, as they need exstensive work put into UI/menus, adding stadiums, overhauling the tactics system, setting up teams properly, creating a believable ML experience and so on.
I don't think Konami is willing to invest in such a task, but hopefully they'll sell it off to another developer soon, as there's been rumours of them selling other titles like Silent Hill and Metal Gear.
A new developer could invest the money and personell and hopefully bring a fresh take on how the game can stand out on it's own.
If they don't sell it off I hope they at least bring in a new director as the current one (Kei Masuda?) hasn't adressed player positioning and is a proponent of the current tactics system.