Yes. Google Apps business model, and all Google Enterprise products for that matter, do not rely on ads for revenue. Google sells their business customers a product and generates revenue through those sales. The TOS protects your data.
Google could easily decide to serve ads to paying customers, and it seems likely that they've left this option open to exercise later.
The fact that they apparently "do not rely on ads" is irrelevant.
There are plenty of existent services that have revenue from customers, but still serve ads (visible examples include: pay-TV, public transport)