I think it's not exactly hoarding that people are doing. I think it's a combination of two other things:
1. I think we have (had?) a finely tuned supply chain for most things. TP would be at the top of the list in terms of supply chain tuning because it's got a simple supply chain (some trees, some bleach, some plastic wrap), the demand is easily predictable (usually), and it's probably all made here in the US, so lead time isn't even a problem.
With a Virus going around, people decide to stock up buy buying an extra 4/6/12-pack of TP. Not a big deal to just buy some extra just in case. But if everyone does it, the finely balanced supply chain that was expecting a constant demand gets hit with a demand shock.
2. Once part 1 happens, people notice it happening. This creates media attention and a FOMO-type / "bank run" type of scenario where people are afraid that there won't be TP there when they need it, so they stock up even more, which just exacerbates the problem.
Pretty much the same story with bottled water.
I'm sure the manufacturers' demand planners and manufacturing folks are hard at work trying to figure out if they need to make more product to alleviate the situation, as well as how much more and when. That is probably hard to predict, although I'm betting that with TP the manufacturers realize that people, in aggregate, probably won't use any more over time, so there will just be an excess inventory in people's bathrooms, and when people realize it's not the End of the World As We Know It, they'll settle down and use up the excess. So TP manufacturers likely will stay the course, as will bottled water people. Hand sanitizer and Clorox wipes and such probably will ramp up production as there will probably be above average use of those for a while.
I'd guess that all of these products can be ramped up fairly quickly (weeks), and I personally think the panic will subside soon, so all in all a short-lived phenomenon IMHO.