My guess is no DL and DCA will not be closed. Our local county health offices are monitoring the situation (Orange Co, Riverside Co & San Diego Co). There have been no new reported cases locally. Practice good handwashing and you should be fine. The 2 confirmed cases in California are in NorCal and nowhere near DLR.
We have a better medical infrastructure than say China, additionally people in the U.S. tend to be too entitled and you would see passholders demand that part of their passes be refunded, you would see those who had trips booked insist that Disney reimburse all travel costs, not just admission.
Then you have the fact that the areas around Disney parks are so economically dependant on Disney and tourism dollars that closing them would end up being catastrophic to the economies in those areas and in California we are so dependent on the money flowing from those areas that closing Disney and other major theme parks could cause a complete collapse of California's economy, which is precarious enough as it is. And the reality is with California having a larger economy than most countries in the world, that would cause major issues for the rest of the country and if the U.S. economy fails, then the economies of many other countries aren't far behind. Yes, closing the major theme parks and tourist locations could see that kind of domino effect if we aren't very careful.
Add in the fact that there are so few U.S. cases as well as the fact that even if you are soemhow infected, which is highly unlikely, so few need hospitalization percentage wise and if you do, chances of full recovery are currently 100% in the U.S. although 1 case the person is still really sick.
Even in the areas with the worst case scenarios, the rate of not recovering is less than 5%.
So, if things continue to be managed as well as they have been there really won't be a major outbreak in the U.S., there really is very little danger of the U.S. parks closing.
Unfortunately there is so much misinformation out there and it causes panics that actually end up causing more problems in the end, like there being a shortage of masks for hospitals because people are going and buying them despite the fact that they won't do anything to help prevent you from getting sick with the Corona virus. But they do help those who are sick not spread whatever they have to others if the person who is sick wears the mask and help with other things in hospitals, so the fact that everyone is out buying masks even if they aren't sick means they are causing the spread of disease more than preventing it.
Throw into the mix that chances are Disney would be required to pay every CM their normal salary and for tipped positions approximately what they would have been tipped during a shut down and it would be so costly that even Disney might not be able to recover from that. And smaller parks like Knotts, etc. Really couldnt if they had the same issues.
We have seen far worse diseases, some of which revolved around the parks like the measles outbreak and that didn't shut the parks down, so with all of the factors, the likely hood of the U.S. parks closing is extremely low. I am not saying it is impossible, but very low, way less than a 1% chance and that is only if we end up with A LOT more confirmed cases.
Also, I know they are working on a vaccine, but then you have people like me that if I get the flu shot, I get the flu every single time and it lasts for well over a week and is extremely severe, but if I don't get the flu shot, I don't get the flu as a general rule and the grand total of twice that I did in 40+ years of not getting the flu shot it was over in 48 hours or less with very mild symptoms. So I would obviously be very caution with any vaccine, even though I am not opposed to vaccines, my body just handles them differently than most people.