We can only guess about the damage done to the WT corporation by the internet because it is on going and will never go away. The Governing Body old fogies took a typical head in the sand approach to it perhaps hoping that armageddon will come or that it would just go away some how. They were very late when it came to using the internet because of their demonization of it.
They are a reactionary Cult and so don't have any real good plans to look at a situation and make appropriate moves to really take advantage of the internet all they can do is disfellowship those members who found out the truth about the truth to avoid a mass exodus how long will they be able to keep this up with any meager success time will tell. Also they may be forced to capitulate on this disfellowshipping form of information control in the future as the courts call them to accounts for some of their cruel behaivor be it through loss of Charity status which could force them financially to give up this not to mention all the lawsuits that have resulted from they way their in house Judicial system handles pedofiles and innocent victims.
I think the damage done is huge but hard to see the present results as many fear disfellowshipping and prefer to remain quite about what they are learning for obvious reasons. To me the problems the internet is causing the WT is like a snow ball rolling down a hill getting bigger and faster as time goes on.