So let me make this crystal clear: ISSUE: Sheep aren't regrowing wool; what's wrong, since it's not that thing that happened after 1.0.0 came out?
I'm not quite getting what the problem is?
If you are running the developer build then sheep will have it's wool grow back.
If you are using standard MC 1.0.0 then sheep will not have it's wool grow back.
Sheep has never grown wool back after being sheared in the past. The first time i heard of it was when you posted and i read about it in the weekly dev build.
So to be CRYSTAL CLEAR:
Sheep will never re-grow their wool and they never have in the past unless you use the development build that was released on Dec 8th this year.
What are you going to do with all that wool anyways? Are you using RP2?
If you are using RP2 then you can cut grass until you find some flax seeds and plant them. They work exactly like wheat but grow 2 tiles high. They drop flax seeds and string.
The reason they exists in RP2 is because of all the wool and string you need to make colored cables and bundled cables.