I think that in the short to medium term, this will definitely have an impact. I could definitely see a couple of years of reduced investment and guest figures while the economy sorts itself out and the parks get their cash flow back to normal levels, but I think the industry as a whole will bounce back to its former self in the long term (5-10 years from now, I bet that the parks will be running as though the coronavirus pandemic of 2020 never happened). If as people predict, we start to see a return to normality in around June/July and there's a nice summer like we've had for the last 2 years, then I think the parks could have a good Q3/Q4 that partially recoups some of the losses made during Q1/Q2. There are of course issues surrounding financial impact on people and appetite for mass gatherings, but the British government have announced a plethora of financial support options to keep financial impact on households to a minimum, and if scenes in Britain last week are anything to go by, then I think that the appetite for tourist attractions & mass gatherings will be stronger than ever once normality returns!
Having said that, I don't think guest figures will fall as much as people predict in the long term, and I also don't think that investment will dry up completely. My personal prediction is that we will see less parks building major rides like coasters than we did in the 2010s, but we will still see them being built. Maybe we'll see investment levels more akin to what we saw in the 2000s, which while there were somewhat less new coasters being built per year than in the 2010s on average, there was still a respectable amount being built each year. Also, most recessions throughout history only seem to have lasted for a year or two, so even if we do have a recession, I'd imagine that the world will have recovered to an extent by 2025, maybe 2030 if we're being very pessimistic. So the parks should have ridden out the storm and emerged stronger by the end of the decade.
As for parks to be worried about; I wouldn't worry too much about any of the major players. Disney & Universal have the financial might to ride out a crisis like this for sure, and provided the efforts to save the worldwide airline industry work well enough, I'm sure that people will be flocking back to their parks in Orlando and across the world in large numbers before too long. Cedar Fair seem to be perfectly stable financially, Merlin recently went private so are likely in a less precarious position, and SEAS have been on the up in recent years with their focus on roller coasters and other thrill rides seemingly working well for them. I can't think of any problems with any of the others financially, either, and I wouldn't worry too much about the larger independent parks (e.g. Europa Park). The only major player I can think of to be worried about is Six Flags, as they allegedly weren't doing too well before the pandemic. If things go badly, they could potentially be headed for a second bankruptcy.
The only parks I would be worried about are the small independent parks, especially ones that showed signs of struggling before the pandemic. COVID-19 may already have claimed its first theme park victim in the form of M&D's, as that park has now laid off all of its staff and is selling Tornado. Even if M&D's does reopen, it shows that they're seemingly struggling, although I don't think they had been doing brilliantly since the Tsunami incident in June 2016. Other names that come to mind are parks like Drayton Manor, which has suffered financial difficulties since the Splash Canyon incident in May 2017. In the UK independent scene, some other names come to mind too. Despite them being a somewhat larger independent park, I'd even say I'm slightly worried about Blackpool Pleasure Beach, as they've apparently been struggling since Icon didn't meet financial expectations in 2018.