Previous games are irrelevant to this topic. HeartGold, SoulSilver, Platinum, etc. were released for the original DS, not specifically the DSi, like Black and White.
I've followed the quest to find this answer for a while now, and all signs point to no, Black and White will not work on a foreign (aka non-Japanese) DSi or XL system.
I was able to purchase a Japanese system and although it may already have been answered by the time my copy of Pokemon Black arrives, I can confirm within the next few days whether or not the game is compatible with a DSi or XL of American release. Again, I'm betting this will be solved before I can get around to it.
I've followed the quest to find this answer for a while now, and all signs point to no, Black and White will not work on a foreign (aka non-Japanese) DSi or XL system.
I was able to purchase a Japanese system and although it may already have been answered by the time my copy of Pokemon Black arrives, I can confirm within the next few days whether or not the game is compatible with a DSi or XL of American release. Again, I'm betting this will be solved before I can get around to it.