They went to Intel for design support with the MP1,1, as they did not have sufficient Intel knowledge in-house. I see no reason why they couldn't repeat that. In 2013 Intel presented its "Group Hug" platform, which would nicely fit to the claimed "modular approach".Where did they find all these Mac engineers to build new Mac Pros, iMacs and Minis if major design changes are coming unless it's more of the same.
They would need prototypes finished, validation testing done, supply, tooling and manufacturing built with late summer or very early fall for October delivery.
And if the next-gen Mac mini's top variant would be bigger, it could be because the high-end mini could double as base module for a Mac Pro 7,1. Synergies and economies of scale. Wouldn't surprise me if the "smaller" mini flavours would be shrunk to AppleTV dimensions then.