I’ve heard this before. The problem is that there’s no consistency. Formats rise and fall in popularity all the time and in no pattern I’ve ever determined. In the past, when other areas were seeing Modern fall off, my area was growing. When Modern in my area was declining, others were growing. Right now, Magic play at my LGS across the board is down thanks to a lot of players leaving the area. The only ones who know the exact state of popularity between the formats is Wizards, and the only thing they’ve said on that recently is that paper Standard is effectively dead.