This site has ~4.5m posts but I don't think that is really a measure of anything. What perhaps is a measure is how long the English language sites have been around. I think this has more to do with the growth trajectories in the English speaking world vs the Spanish speaking world.
Things are pretty much on the decline for the WTS in the west or at least stagnant which is why they are looking elsewhere for growth. There are fewer people who have lived the life for long enough to feed the supply of leavers in the same quantities right now but that will change once they get past the initial growth and into the churn where growth slows but they still keep making converts simply because not enough people have been immunised against them.
This is where having information available will be a huge bonus - imagine having freeminds and jwfacts 10 or 20 years before their time? That is what the Spanish world can effectively enjoy which has to do a lot of good.
Of course, the world is different and the society is different and the WTS teachings are different, how many people are online may be different ... so there are no guarantees that what is convincing and important to us is viewed likewise for others. But it would be good to have the information out there for anyone searching.
BTW: The language / posting constraint is purely for practicality of being able to moderate and protect against people posting obscene / libelous content that we can't 'see'. I would really love to be able to allow anyone to post in any language - maybe one day ...