well we don't know who he would play if he is Han Solo's son. To assume he would be Jacen solo is a bit premature at this point as we don't even know if they will do the Solo twins. There is no real reason to really think that they would
We know it's going to take place about 40 years after ROTJ and it is NOT based on any existing EU story.
In the EU 40 years after ROTJ both Anakin Solo and Jacen Solo are both dead.
Didn't say anything about him being Jacen or Anakin. They aren't going to follow the EU stories. At best they pick a few character names and similarities and plug them in the movies as some geek easter eggs.
When I think of characters like what Cooper would be playing it's as original characters no one has seen before.