I think eventually it will, but problem is we will never know about it.

Previous original releases often where tied to a platform, but I suspect Echoes of Wisdom will keep selling being played on Switch2 for many years. Not as a Switch2 re-release, but simply the original.

Nintendo usually only updates salesnumbers if a release sold more then 1 million in a given fiscal year. So if in future years Echoes of Wisdom will do less per year, we do not get updates.

Probably not, but 5 million to around an even 6 million seems likely.
And I don't see it surpassing games with remakes or re-releases, but you already said that doesn't count for this question.

I hope it does well, do we have sales figures yet for outside of Japan? I was hoping it would beat the Awakening remake but I have a feeling it won’t…I feel like the more casual Zelda fan won’t jump on this one as quickly and sales for games in the later years of a console seem less I think…hope it manages 4-5 million at the least.

We have a few numbers; it opened at 33,000 in Spain, and in the UK it opened at #2 on the charts, with 14% less physical copies than the opening week of the Link's Awakening remake, though probably more overall as digital sales have increased a lot since 2019.