I agree here with Ticker
And the question is do they want to go mainstream?
All mainstream religions are really goingg down very quickly in church attendance etc. (lotfaster then the JW's appear to be doing now)
A lot of people are in the WTS for not being a mainstream religion.
They could loose those people, and have little to gain at the other end of the spectrum, where there are many other religions. They fill a void in the extreme end now.