Originally Posted by psylockolussus
The thing about the younger version is, they would be always seen as the "younger version" where as Famke/Halle/Patrick/Ian/Marsden/Kelsey/Rebecca will be seen as the original version and the one set in the present timeline. And appearance of them except for Rebecca, just made it more clear to the audience.
Unlikely. Fassbender, McAvoy, Lawrence, and Hoult exist as far more than just the younger versions of those characters. They are established and popular characters in their own right.
The same would be true of Young Jean, Young Scott, etc, unless their characters were botched in some way or they were turned into afterthoughts. Give the audience reasons to care about them and they will.