We know that Apple is going to transition at least some of its Mac lineup to ARM-based processors it has designed itself. And we're pretty sure that the initiative will be announced to developers during the Apple WWDC (Worldwide Developers Conference) keynote later today.
However, the latest rumours from analyst Ming-Chi Kuo suggest that Apple's first machines to run on the new underpinnings will be the next MacBook Pro 13-inch and a redesigned iMac, both late in 2020. Kuo suggests that the Intel models will be discontinued at that point.
For our money, that's firstly too early for a refresh of the Pro, while we also think its a little short-order for Apple to expect developers to get things sorted as they will need to ensure app compatibility (although, as with the PowerPC to Intel transition 15 years ago, there will probably be a transition period thanks to some software that ensures compatibility). We have previously heard that the first Macs with ARM processors are due in mid-2021 which seems a lot more plausible.
The fact there will be a new iMac is likely - we've previously reported on such rumours which concern a thinner-bezel iMac. And it could be that an iMac Pro refresh will appear much sooner.
Kuo suggests performance improvements that are significant over the Intel equivalents, while saying that all new 2021 Macs featuring the new chips. Again, we don't think this will apply to the entire range.
We'll find out the first step in Apple's Mac ARM transition later today.