There was a Metaculus question that opened in early April about "How many COVID-19 deaths will be recorded in the month of April, worldwide?" The community prediction was 210k (50% CI: 165k – 288k), which seemed little different from just extrapolating the trend of reported deaths. I saw that countries had all gone into lockdown a while back, so I predicted 75% that the numbers would end up below 193k. The resolution was 184k and I won a lot of points.
Trend extrapolation is only half of what's important. If the trend is foreseeably going to break because circumstances are changing, we need to factor that in. If avturchin is right about the recent numbers being linear with 100K cases a day (I didn't look this up), then we can say that it'll probably take longer than 60 days until 10M confirmed cases. In the majority of locations, R0 is below 1 and many people are recovering (and PCR tests only catch active infections). Of course, case numbers may go up again, which can happen surprisingly fast. Still, I think the mark for 10M confirmed cases is unlikely to be hit before August. Unfortunately, I suspect that we will hit it at some point later in the year when cases go out of control again in some parts of the world where there's extensive testing.
UPDATE June 12th: Seems like I got this one really wrong. Daily new cases are at 135k now, so a substantial increase in cases.