My guess, the 2020-21 NHL season will be truncated and feature a 45 game regular season and full playoffs.
Shortened regular season to account for the delay to the 2019-20 season completion.
45 game because they've done something similar during the last labor dispute with 48 games in 2012-13.
The season will start in December with training camps and officially start mid-January as it did in 2012-13 with the 1st regular season game was played January 19th.
Playoffs will follow the regular format with best of 7 series.