Ok, here's my take on things...
Scores dropping to 450 seems unrealistic at this point in time. There are too many applicants in the pool at 460+ that need to be removed from the pool first.
However, high 460s does seem like a possibility. Anything above 450 is generally difficult to achieve. That being said 440+ generally means an applicant is University-educated with at least 1 year of experience. Since EE first started these have always been favourable candidates to immigrate to Canada. In relation to implications that IRCC is skipping draws to keep the CRS above 470, that seems a bit unrealistic... but never say never. Alternatively, they could have been forced to postpone a planned draw on the 18th in reaction to the pandemic, and were rushed to implement new procedures to allow continuing intake of applications. If that were the case then a PNP-only draw makes sense if they wanted to limit the number of candidates. This would allow them to test new procedures for handling applications on a sample group before implementing the changes more broadly.
Anyway, back to why I think a high 460s draw is possible...
For an outland applicant achieving a CRS of 470+ is difficult unless you max IELTS, have 3 years experience, and ECA equivalent to Masters.
For an inland applicant achieving 470+ is difficult without at least 1 year of Canadian experience or an LMIA-approved job offer.
With the ECA and language organisations suspending operations, and employers not likely hiring and letting people go, there's going to be a slow down in people entering the pool for the time being with the required language results, Educational equivalency, and possibly some who won't meet work experience or settlement funds because of loss of work.
There's also the possibility that people may decide that due to the current situation they will postpone any major plans until things are more certain.
This also relies on IRCC, who will need to maintain regular draws in order for the points to drop. Unless they come up with a system to handle the 7000-8000 ITAs they issue per month they may choose to suspend draws. Or draws may become even more irregular, with longer gaps between and erratic numbers of ITAs being issued, based on how quickly they can process applications at any given time.
With no comment from IRCC as of yet, we can assume that, once they have implemented new procedures to handle applications, they still intend to work toward immigration targets (which they confirmed only 8 days ago).
I feel really bad for anyone who has had their application put in jeopardy because of COVID-19, and hopefully things will turn around soon and we can get back to business as usual. We all know how stressful this process can be. Stay healthy all and here's hoping things change for the better asap. The above are just some of my thoughts in regards to the developing situation.