There isn't a brick limit really now.
you can go over the brick limit, its just once you get like ~400k bricks stop rendering.
The ghostIDs are transmitted using 17bits. 2^17 = 131072 ghosted objects at a time. Due to bugs in the ghosting code, if you have more objects than that, you may have problems like not seeing other people or not being able to respawn. Even if it works perfectly, you won't be able to save everything at once from the client because not all of the server's objects will be represented on your client.
If I recall correctly, badspot said if people start hitting the brick limit, he'll raise the limit on bricks. Anyone else remember that?
I have no idea what Badspot did to make it increase.
Another bit changes 131072 into 262144.