The IP is dead because, even as per the example of Default and its successes in the west, SE doesn't care about it. Nintendo were the ones who made it a success in the west by publishing and marketing it heavily as a must have RPG for the 3DS and throw back to FF of old.
I don't understand where this budget stuff is coming from? Did we ever get a budget comparison between original and sequel, or was it always a low-budget effort?
Bravely Second might be a failure in Japan but it remains to be seen what it can achieve in WW sales.
My point is that it is just too soon to start calling it a successful IP. Actually, it is too soon to call it a dead IP since its fate is still uncertain. But if SE has shown anything, it is that they don't have any interest in continuing it. Otherwise I don't think they would have developed Project Setsuna, which targets the same demographic as Bravely Default.
As for the budget discussions, the sequel is built on reused assets. That, a good budget, does not make.
I'm only half joking when I say that Nintendo should just take over the IP, lol.