Cash wise , the WTS have always been restricted by Russell's infamous statement that ( paraphrased ) "When we have to solicit funds , it is evidence that Jehovah is no longer behind the work and it is time to stop printing the Watchtower". I've heard a couple of the WTS financial guys say that this has tied the WTS hands and made it very difficult to openly ask for donations. Notably it has been a while since the WTS has drawn any attention to this statement , and they are possibly hoping that the R & F forget about it.
The WTS also does not have the wealthy profile of members required to bankroll the work. I remember when I processed the Gift Aid donations from the Inland Revenue in the UK for the congregation and receiving in error the return for a neighbouring church and was gobsmacked to see the huge donations that were being made. Most JWs have relatively low income and capital ( due to the lack of a college education and a failure to invest in long term assets such as shares or property ).
I think that it is inevitable that there will be more emphasis on each individual congregation mandating a monthly payment to the WTS (and not just the £10 or £20 per month that most do at the moment). An obvious move would be a letter "encouraging" (ie demanding) a £X per month per publisher requirement from each congregation in the same manner as congregations currently donate to the convention and circuit funds , presumably "sold" with reference to growth in the 3W (as there cannot be an open correlation with the literature "purchases" and donations).
Something along the lines of this letter would open the purse strings...
Dear Elders,
We appreciate very much your current resolution of £10 monthly towards the worldwide work.
As you will be aware , the cost of raw materials , property and fuel continues to escalate. Jehovah is also greatly blessing the work in Africa and Asian countries and we have an huge ongoing Kingdom Hall and Bethel building program that is largely financed by contributions from overseas. Many brothers have willingly given of their time and labour in such projects , but many who are not in a situation to do so have asked how they may assist the work in a material way.
Many congregations have reviewed their monthly contributions to the Society to better reflect this need and we are suggesting that a contribution of £10 per month per publisher would allow us to "speed up" the program and greatly benefit our brothers in these lands , as well as more adequately serve the needs of the work in our own country. You may wish to consider your current donation at the next elders meeting.
We know that Jehovah will "open up the storehouse" and greatly bless his people at this time and we pray his rich blessing on all your activity.
Yours faithfully,
WTBTS