Maxis has shared the recommended system requirements for The Sims 4 for Windows.
REQUIRED: Internet connection required for product activation.
OS: 64 Bit Windows 7,8, or 8.1
PROCESSOR: Intel core i5 or faster
AMD Athlon X4
MEMORY: 4GB RAM
HARD DRIVE: At least 9 GB of free space with at least 1 GB additional space for custom content and saved games
DVD-ROM: DVD ROM drive required for installation only
VIDEO CARD: NVIDIA GTX 650 or better
SOUND CARD: DirectX 9.0c Compatible
DIRECTX: DirectX 9.0c compatible
INPUT: Keyboard and Mouse
Based on these specs, the closest analog Apple has for their personal computers is the current iMac model, in production since 2013. This iMac model also uses the Intel Core i5 processor, and matches or exceeds the other system requirements for Windows PCs. If you have an iMac from last year at the oldest, and 9 GB to spare, it will be all you need to play the game when it eventually comes out on Mac.
Maxis has also teased a livestream this August 26, at 12 PDT, on their Twitch channel. You can watch the stream here.
The Sims 4 will be released on Windows on September 2, and on a still unannounced date on Mac.
