They're saying he's 'tempted' which is pretty much reported by every Italian outlet.
Lets see what we got right now
Certain
Chelsea offers a 'significant sum'
Marotta said no
Marotta said we dont keep players against their will
somewhat reliable
La stampa : Juve offers to nearly double his wages
La Stampa : juve doesnt want to sell and tries to see if they can get the player to extend (ergo, if he refuses well sell him, despite 2020 contract)
La Stampa : He's tempted by chelsea. Wel sure. Means he has not yet decided.
Other media
EPL tabloids : Sandro told his management that he doesnt want to renew.
EPL tabloids : juventus accepted the deal and its close
Seems pretty clear to me.
Juve wants to keep him by extending his deal. He's haggeling for the best possible deal.
If he overplays his hand or refuses a new deal, we'll sell him to chelsea for a huge sum