I am not sure how long that can persist, though. One of two things is going to happen:
- The costs/devtime will add up such that FTB has to monetize (or take a ton of donations?).
- The site, launcher and modpacks will be neglected such that no amount of community awesomeness will fix them.
Have you looked at the technic launcher? It is a very, very good piece of software (in the sense that it works and has a sound model). It may be a cruddy pile of PHP and some awkward Java, but that doesn't matter if it wins a capability war. Having one or two of those modpacks do big updates without 100mb downloads will show you how good a launcher and updater can be, and it is better than what we got here.
For now, I think, FTB enjoys popularity because of its personalities and its close association with Forgecraft. It's hard to say how long that'll persist, though, if things continue as they are. Especially if Technic starts executing on their charity strategies and makes money.