Nah, still privacy, imo. Scaling is an incremental issue that will never be truly “solved” and there will be 1,000 different “solutions.” Lightning will be a ~50x scaling growth for payments at full adoption probably, but we have numerous technologies that will give another order of magnitude benefit.

The reason privacy is the biggest issue is because dissidents need high assurance privacy RIGHT NOW, to literally protect their lives and their families. Where as we don’t actually need to scale to 2 billion users right now, because 2 billion users aren’t desperately trying to use it. The idea of bitcoin is still getting through the Overton window of the vast majority of the world. That will come in time.

Privacy is the more pressing concern, imo, scaling will come in waves that follow the waves of new entrants.