I asked in the DS section, but the breakthroughs in TWL_FIRM on 3DS are not likely to lead to anything on "real" DSi hardware, so be careful with that DSi and don't brick it. Not that it matters that much, content wise, but it's just hard to have to admit defeat on the part of the scene where the DSi/LL/XL goes.
But you never know; maybe one day there will be a new flashcard that -using software or a small button/switch- can be put into a DSi compatible mode (like CycloneDS iEvolution) as well as regular 3DS mode and a DSi kernel exploit (by analysing possible avenues with a decrypted TWL_FIRM) for DSiWare installation. We've had plenty of hoaxes, but if some group can pull it off you have the #1 card to have on DS, DSi and 3DS.