I think this remake may slightly outperform the original Diamond/Pearl sales. I would project between 18 and 20 million units sold.
Bonus question: I played Brilliant Diamond and I really enjoyed it! They fixed the main flaws of the original DS games, particularly the battle speed. I beat the Elite Four and Cynthia for the first time after 48 hours of gameplay, and I've played another 10 hours of post-game content, and I haven't even started to hunt legendaries at Ramanas Park yet. I spent most of my playthrough in the Grand Underground, whether it was catching various Pokemon or collecting rare items.
It sounds good when you say "For the People", but what you really want is... a stronger army than the Knights, and the evil power to control the people.
(Ramza Beoulve, Final Fantasy Tactics)