Don't know if it will hold up or not, but I was just at Petit Jean State Park yesterday and the color is quite good, and the waterfalls are running great - we seldom get both at the same time here. You can see a few images at: http://www.cloudland.net/currentjournal.html
I've also heard there is good color elsewhere in the area, although if it rains all week it may knock it back quite a bit. I'm headed down for a few days myself and will roam around wherever I can find any color. Hope you have a great trip!