With 2020 settling at around 28.2M (I think a few regions will pop once we get Nintendo official data, so still chance at above 28.5M), I think there is room for growth in 2021. US/Europe IMO can go 5-10% higher than figures achieved this year (better software slate / revised model / better and more consistent inventory / better pricing during holidays). "Other" regions has even more room than that. Japan best case IMO is flat, more realistically 10-15% down -- its hard to match the impact of a title that cruised to #1 all time in the market in just a few months.
Covid bumped hw dramatically last year, most likely Switch will be down massively due to 2020 insane performance. Above 20M is locked.