Wow, this was a surprising poll. There's more people voting for 2021 than 2019.
I think the best possible time to launch would be March 2021. Copy Nintendo's strategy of getting launch sales, and a holiday sales boost all in the same year. But they don't do that. So definitely Winter 2020.
2019 feels like it would be a weak underwhelming system. I want a $500 console in 2020 that pushes the envelope as hard as they possibly can. If I were Sony, I'd stop including a controller in the box, and make PS5 backwards compatible with PS4 controllers. That would squeeze an extra $30 to $50 of the price towards more power. Whether I pick up a PS5 at launch is entirely dependent on the price to power ratio. If you can build a PS5 comparable PC for the price of a PS5, at launch (price of windows, 3TB HDD, and reputable parts brands included), then I'll wait for the price to come down.