How many engineers does it take to start a VM? About 3000 .
It's too early. Managing one big codebase and a growing number of developers is challenging. But once you separate the services, it gets way harder to move functionality between them. You don't know yet what the proper breakdown is. You can theorize, but you're probably wrong, and the cost of being wrong is high.
Additionally, you have to put team boundaries where your service boundaries are , and it's even harder to move people than it is to move code.
You're better off keeping the big codebase, and waiting for clear divisions to appear. Watch for naturally forming sub-teams of developers. See what they're doing. By the time you draw the service lines, they should be merely formalizing the divisions that have already appeared.