Welcome to New Hampshire. Mine looks the same. The rest of the rockers are very solid though. That pillar is structural, but if that's the extent of your rust it's not horrible... yet. This year I plan on cutting out my rockers, reinforcing all the pillars and putting in boxed steel rockers.
Actually on a second look, pull the long kick panel off and inspect behind that too. It may not have gotten to the structure yet.
The "Mall Crawler" - 1998 ZJ Grand Cherokee 5.2 V8, 5.5" LongArms, 32s, 12000lb winch & more.