It could be both: a new live-action series of one of the five arcs or a brand new story, & an anime about some 30-something women who've been fans since their childhood but have now become working women or housewives facing various problems such as the conflict between their career & family, looking after kids w/ psychological disorders, infidelity of their husband &/or themselves, the burden of being a single parent, the anxiety & family pressure of still not getting married, etc. & seeking refuge/guidance in their childhood favorite show. As tokusatsu & anime are separate depts. in Toei, they could simultaneously handle both shows.
It absolutely inadequate to compare mahou shoujo anime to THE shounen anime. It is like comparing Black Widow to Aquaman. This is reality, I am not misogynist but men are way more into these stuff and stick to them way into adulthood. In Japan the separation of men and women shows are still a thing and as much as we are trying to stop this in the West the box office show the same result. As for Doremi - it is a much better comparison, but the movie was the first new anime for the franchise in a long time, while Eternal is the forth season of an ongoing already flawed reboot posing as a movie. I highly doubt Doremi would surpass Sailor Moon if Crystal started as a movie anniversary project. To be perfectly honest it is not all bad that Eternal underperformed as it was also underfunded . Otherwise it would encourage TOEI to keep it this way - something they actually do pretty successfully for years.
In the Usagi's Birthday Party on June 30th 2020 they didnt show a trailer of Eternal ( we already had seen a teaser of it ) but the full Moon and Chibi Moon choppy transformation. Maybe it's the same with this year and they just show the Eternal Sailor Moon transformation ( of course retraced from the 90's ) and they leave the proper trailer for September.
In fact: they shown the final trailer for Part 1 in October 2020 ( with a japanese release in January 2020 ) and the final trailer for Part 2 in January 2021 ( just one month before it's premiere ).
Yeah, those wings in the 90s anime obviously have a considerable thickness, & are also shown to be made of hard materials in that they can easily knock things down to the ground if she's not careful. lol