Why would a mac need a micro usb port? This is about power adapters.
So you'll just need to buy:
- 1 power thing with USB opening
- 1 cable
if you want to charge (or transfer data) you need 1x USB micro -> USB cable for your PC/Mac (exactly like you need Dock -> USB now).
[For the people that still are fan of the dock after reading.... think of all improvements:]
- 1: every phone has USB all of the suddon.
Wow: all accessoires can be used on only mobile if it has micro usb

Just need the software to work. (hey: yeah... i can connect a printer from my computer to my phone all of the suddon!
- Everybody (not only apple, but also nokia, siemens, etc. customers) can buy the same stuff to charge a phone. making prices lower, more efficient stuff etc. Hey: If i'm in my friends car, who has an android, I can charge my iPhone 4!
Will it cost money? Nope.... old phones still have old adapters.
If apple is smart, they support both dock and micro-usb for both data and charging in a sort of click in system. Dock only for backwords compatibility to their old accessoirces. And micro-usb for the improved world of mobiles.
If apple is smart they bring out the best charger in the world, that consumes no energy when it's not connected to a charging phone, and they earn a lot of money on these new devices.