Eh? Don't you mean 3 years for all 6 updates?
2021 - 0.1 and 0.2
2022 - 0.3 and 0.4
2023 - 0.5 and 0.6
So if we're keeping the 2 updates per year sched and the plan is for something in between 12 and 20 updates, you're looking at an additional 3 to 7 years of development time...bringing the total to...
/crunches numbers
...somewhere in between 6 to 10 years worth of dev time, total.
(Personally I still think he's going to target 15-16 updates total, since that still falls under the "in between 12 and 20 updates" target. Anything beyond that feels overkill, but that's just my opinion)