Predictions:
The Mac Mini is dead, will be replaced with a new screenless Mac, simply called Mac. The Mac Pro will eventually be a variation on that case design.
The MacBookAir is dead, will be replaced by a new baseline MacBook, simply called MacBook, that looks like the existing MacBook line but slightly larger and cheaper to produce. The refreshed MacBook line will come in 2 variations: 13" entry model with a larger body, bigger bezels, entry level specs and a 12" model with the existing MacBook slim design with higher specs.
They can get it to $999 if they streamline the production process. It's been 3 years since the introduction of the slim MacBook line and like the MacBookAir which started off as a premium priced Mac and ended up becoming the budget notebook, the MacBook's manufacturing is becoming standardized and a larger body would make it even easier to produce.
The Mac line would then be:
Mac
Mac Pro
iMac
iMac Pro
MacBook
MacBookPro