Besides speculation and personal desires there are the facts:
* Long delayed update, means: full redesign or death of line (I bet on redesign).
* Apple now refocused it's marketing, evidence it's the cheaper iMac, the oversized iPhone 6+ (an sacrilege a year ago).
* First batch of Broadwell-M aimed at tablets and desktops (quote Intel)
*44W TDP limit on current Mac mini keep it away an decent Haswell cpu (65W).
*Users (specially those on music production) wants a fanless Mac.
* the gap among the Mac mini (and iMac) with the base Mac Pro it's huge.
* Apple needs a descent gaming Mac to boost game sales at the app store.
× Mid range desktop are replaced twice fast than Pro desktops, so if an xMac eats some Mac Pro sales, it's very likely it's owner will update it sooner than if where a mac pro.
The mini would eat some iMac sales, maybe but at low end each $ accounts, the mini option always have means the first choice, then providing the users freedom to upgrade to iMac or more powerful desktop (name it mini Mac Pro or xmac) doesn't means loss of earnings since Apple simply translated an bigger margin to its headless units.
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So, from my pov split the mini to two more specialized range of Macs it's the winner choice, providing an also cheaper entry point, while providing a competitive solution on the Mid range (server, gaming, Pro sumer).