This will be his 1st full season as 1st choice alongside Jags, he's still learning. Look at Zouma; one of the brightest defensive prospects in world football before he sat on Chelsea's bench. I hope for your sake Stones can kick on but he won't have time to make the mistakes of which he's made plenty of here. It's a year too soon in my opinion. A couple of bad games and he could fall out of favour with Jose, someone who doesn't give many second/third chances; Cuardado being the latest example. Stay here, prove that you're one of the best in the league/Europe, go to the Euros as 1st choice for club and country. He could have his pick beyond Chelsea next summer.
On the topic of Holgate, I'm sure he'll become 'one of your own' should his career kick on and maybe produce another big sell-on percentage one day - us football fans are a fickle bunch!