It seems a Billion Road Switch and PC release date has been pinned down, if two product pages are to be believed. The Nintendo of America, Nintendo of Europe and Steam listings now say the game will be released on April 16, 2020. [Thanks, Gematsu!]
Back when the Billion Road localization was announced in November 2020, it had a Spring 2020 release window. That was eventually narrowed down to March 2020. Now it appears April 16, 2020 could be it.
Billion Road is a sugoroku game along the lines of Animal Crossing: amiibo Festival and Princess Maker Go! Go! Princess. It is a board game where up to four people attempt to travel around Japan, investing in different businesses and hopefully turning a profit. In addition to becoming rich, collecting different monsters from around Japan and using them to hopefully secure a spot as one of the most illustrious members of society.
There are also different modes in Billion Road Switch. One is the quicker Skirmish Mode. It lasts three in-game years and tasks you with swiftly making money. The Tournament Mode is more intense and might bring to mind long Monopoly sessions, as it runs for 30 in-game years.
The Billion Road Switch and PC product pages now both state the game will be released outside of Japan on April 16, 2020. It is immediately available on the Switch in Japan.