naturally Chris Pratt's name gets bandied about a bit as a replacement for Harrison, but while I'd be happy to see him don the fedora as a new Indy, there really is only one Han Solo

The thing that scares me the most is that Han was around 29-30 years old in the original film so to realistically recast a younger version they'd have to set the story at least 10 years before the events of A New Hope, i.e late teen to 20 year old. Too young and immature to be the cocky, cynical rogue that is the basis for his character, and I honestly have no interest in seeing his formative years. I really don't see him becoming 'Han Solo' until well into his mid 20's.

I do remember reading that they were having trouble developing a Boba Fett vehicle because of his anti-hero status and there were worries how they could make him the protagonist without ruining his character in the original films, maybe this is their way giving Boba Fett a major starring role with Han Solo as the focus.