I would be surprised if Apple goes back into building servers, even for their own internal use. Apple makes extensive use of external cloud services, even to provide their own "iCloud" services:
Breach of contract, false advertising, unfair business practices sueball fired
www.theregister.com
The iPhone maker pays $30 million a month to use AWS, CNBC reports
www.theverge.com
It's true that they have reduced their use of AWS recently, and are using their own data centres more, but I expect it would be a massive undertaking to replace the x86 Linux servers with M1-based machines running virtualized ARM-Linux.
It's conceivable that they might have some specialized services running home-grown Apple Silicon servers...but I think it more likely they would use commodity servers, maybe with more emphasis on ARM machines, as these become more prevalent in the industry.
I would love to be proven wrong...but I just don't think Apple wants to go back into enterprise server manufacturing or to become a generic Cloud Platform infrastructure provider competing with Amazon, Google & Microsoft.