From the released list of current and future 5*s it appears that there are no plans for the following champs to get a 5* version:
Abomination
Black Bolt
Black Widow
Captain America WWII
Daredevil (Netflix)
Dr. Strange
Electro
Joe Fix-it
Magneto Marvel Now
Ms. Marvel
Scarlet Witch
Thor
The Vision
War Machine
Wolverine
I think they exclude champs from having 5* versions for one of three reasons:
1. They are a reskin champ or they have a reskin champ (Abomination, Netflix Daredevil, Mags Now, Ms. Marvel)
2. They are a very useful champ (Black Widow, Electro, Thor, Vision, Witch)
3. They used to be considered a very useful champ (Strange)
Captain America WWII and Wolverine fit both criteria 1 and 2.
War Machine and Joe Fix-it may fit criteria 1, but I don't consider them to be as much of a reskin as the other champs.
Black Bolt doesn't fit any criteria, not sure why he is excluded. I would guess that Black Bolt is getting a reskin. But he doesn't fit in the upcoming chart of 120 champs (which is really only 112 champs btw).
One flaw to my theories is that they released both Iron Man and Superior Iron Man which are very close reskins and they are releasing Cyclops 90's which is an exact reskin of Cyclops xavier. Also, they are releasing all of the Spidey champs as 5*. So...
I am most bummed by the release of Cyclops 90's as he is exactly the same as the ugly Cyclops.
I am most bummed by the non-release of The Vision. He is one of my favorite champs, and sad to see that he is not getting a 5* version. I guess they will be selling OG Vision for $$$$$.