I can't predict "completely automated" but I expect that for B2B purchases the majority of the process will be conducted by AI agents. A human working at a company that is seeking a service provider or complex piece of software will write a "tiny RFP" in the form of a prompt, and an AI assistant armed with knowledge of the company's needs, budget, and context will conduct independent research and pull togther a shortlist. If it has questions for solution providers that aren't covered by their available content, such as case studies or reference accounts that match the company's profile, it will converse with the solution provider's AI Agent, which is trained on its entire knowledgebase. It might be possible for the solution provider's Agent to give a demo to the company's AI Assistant, and the assistant can summarize the demo, including key highlights, and include them as part of the shortlist.
I'm not willing to predict that AI will make purchase decisions for items with large pricetags but I can absolutely see a world where 75% of the source selection process is entirely automated and happens over the course of about an hour.