Google has created so many products and services over the years and we can see that most of it's products needs Google's support to function properly.
So even if Google has it's own cryptocurrency, it will keep it Centralized in order to fetch more data from it's users and keep tracking them to the eternity.
The one who owns the right information will always stay ahead in the race. Google owns the right info and a pretty significant part of the services we're using are provided by them.
There's no point in creating a decentralized coin when you can create a centralized one and store even more information about your customers than ever before. This is how they've been feeding themselves for so long, they're just going to continue.
But a Google coin would probably be advertised as decentralized one way or another, creating a fake decentralization aura around it. Just like that Blockchain Messenger on Android made me believe for weeks, until I read more about it, that all messages are stored in the blockchain and it's fully decentralized..