Well, it's complicated, isn't it.
For years the bOrg preached anonymous, voluntary giving (not a reality in some situations, but they always tried to paint it that way) ....... but now, having bitten off way more than they can chew financially (and before you add in all the legal costs) a way is needed to tithe. They have to do it, somehow.
"Sir82: I don't know that they would do it for everyone, but I can easily imagine that it would become a requirement for being appointed as an elder, MS, or pioneer.
I.e., only those who tithe get "special privileges".
Sadly, I think this is where it is all heading. You can't get anything extra these days (cart duty, permission to go to the International Convention, work on the KH builds, etc.) unless you "qualify", so why not sell these privileges for a tidy profit? Take a page out of the pope's playbook --- wait --- If they could sell guaranteed entry into paradise THAT would really be a money maker.
Otherwise, just going with straight tithing is problematical when all the JWs (here, at least) are poor AND rely on unreported cash income just to get by.