Finding a new way to get more money from the sheep is on their agenda. What the next form that will take is not certain but I don't think it will be a set policy of tithing, although it may be suggested.
The JW religion is more about being a works based religion so it would be hard to continually sell this idea of tithing. They need to come up with the an idea that will make it seem that JWs are providing a sacred service which is clearly identifiable, not just by giving 10% of their income.
Here's some comments that they have made about sacred service -
W 76 10/1 re Sacred Service
Par. 5 “So their doing something of a sacrificial kind would be out of the ordinary, something not carried on in general by the unchristian people of this worldly system of things.”
Hebrews 13:16 16Moreover, do not forget the doing of good and the sharing of things with others, for with such sacrifices God is well pleased.”
W80 8/15
Par. 3 “Obviously, this has to do specificially with service to God, done out of appreciation for sacred things – something out of the ordinary that calls for the sacrifice of time and energy.
God's Kingdom Rules
Yes, relief work is a valuable form of sacred service.—Rom. 12:1, 7; 2 Cor. 8:7; Heb. 13:16.
W 06 11/01
Building Kingdom Halls is an important part of our sacred service
W01 3/15
Of course, Bethel is primarily a place where mature Christians render sacred serviceto Jehovah and work in behalf of fellow believers throughout the world.
They've come up with their own logo, JW org and it can be seen wherever JWs are. JWs see it as part of their preaching (or sacred service).
They've also thrown the JWs into the public with their public preaching work and even shopfronts on occassion or stalls in certain areas. They've started to dwindle down the importance of house to house work.
Their next step might be to tell JWs that part of their sacred service will now include time set aside to earn money with the specific purpose of donating it to them. They could leave the option of how to do this to the congregations but encourage them that whatever it was, do it in a united way together and with the focus that all money earnt be given to them. The responsibility of how they did this would be completely up to them and that means any taxes/permits/licenses/insurance/complying with laws could not be held against the WTBTS, they would be doing it independently.
Suggestions such as lamington drives, joint garage sales, sales of other goods produced and sold in joint effort, even small businesses where all profit would be donated. It would need to be all of the net profit otherwise they are doing nothing out of the ordinary (the sacrifice wouldn't be great enough to constitute sacred service)
They could also sell this to the sheep if they advise them that they could include a small JW literature stand at their stall.
Because all profits would be going to the WTBTS it would be considered as sacred service and although it may mean less hours in field service, would satisfy the JW's need to be seen as doing 'works befitting a christian' with blessings attached. Working in groups would also be seen as a a 'fine and uplifting' christian work.