I guess that is the thing, what time frame are we looking at? I've seen reports that have suggested it could last till spring 2021, so basically lets take it as 1 year. I still think for it to reach 80% infection rate within a year would take something colossal to happen, because so far the infection rates are phenomenally lower than that. I've also read reports that the virus might become seasonal, but weaker as people build up resistance. So again maybe 80% will get infected, over a long period of time but with varying/weaker strengths of the virus. I'm not trying to dismiss it, it is very serious, but 80% infection and 1 million dead seems unlikely to me given that the places that have experienced the worst of it so far, aren't anywhere near those figures.
Two things...
1. The main thing is you're ignoring exponential growth. These things start small "Oh there's only X people with it - there's nothing to worry about!", but the number doubles every 6-7 days. So 1,000 today is 2,000 next week. Then 4,000, then 8,000, then 16,000, then 32,000, 64,000, 128,000, 256,000 and 512,000 etc.
In 10 weeks time you have 1m people infected (or who have been infected). Then think about the week after that and the week after that...
2. "the places that have experienced the worst of it so far, aren't anywhere near those figures" - this hasn't actually started properly yet.