No recasting for the 7 8 9 sequels. Use the original actors if they are in the final script. And use the original characters only if they have something interesting in therm of role. If it's just for a cameo ala first Expendables movie, then better not use those charcaters at all.

That said. Once the sequel trilogy is done. Maybe, just maybe, we could back in time and have some fun Han and Chewie adventures with new cast. I'm not really sure about that, but I could see a recasting only for earlier adventures of our heroes in standalone movies, IMO.