I cruise solo a lot. For the most part prices drop after everyone's final payment is due. Having said that if there is something you really want book it. I do both. I am booked for Iceland next Aug. It's pricey, especially when paying in Canadian dollars, but it's a cruise I want.
As for Covid. I have done two since covid started and am lucky both where during lower peaks. It is crazy right now and glad I am not going. Plus there are those entitled people who do not respect rules. ie on excursion in closed areas where they say "you must wear a mask" and people don't.
I say if you find what you wank ahead book it and start saving. If you want to wait, it will likely drop but then flights could be an issue. Best of luck.