Transfer news is always about a day behind where it actually is.
City will have presented the £100m offer to Villa and offered personal terms to Grealish. Villa will have likely said to City, "Okay, £100m is fine, but let us table some terms to Jack first and if he says no then you can have him."
I imagine Grealish took the day yesterday to either say goodbye to his friends or have one last think while on home turf, and he'll have made his decision already. We'll likely find out the truth tomorrow or Wednesday.
He's a human being. He's been at Villa since 2001, when he was 6 years old. Whatever decision he makes is going to be an emotional one and I imagine he's discussed it at length with those closest to him.
Whether it happens or whether it doesn't, he'll have thought long and hard about it.