@redriderbob dropped this straightforward answer(lots of confusion on this with calendar year vs model year, people making their on numbers appear out of nowhere, misunderstanding refresh vs all new, etc.)
5th Gen HD will be in 2022 model year. During the refresh of the DT models.
So, will be interested to see what they do to the 2019, then 2020 I will be prepared to make a decision on a used Rebel, while I wait for 2022.
We will probably buy our new camper spring of 2020 calendar year. We found one that will be a compromise on payload with the 1500, but would easily work for 2 years til the HD debut and inaugural working out of the bugs.
Now to stay patient and work the plan.