Keep the DS and GB games.

Sell the DSi.

You're literally getting no added benefit from it because a 3DS will do exactly what your DSi can do, plus play 3DS games. Your DS Lite has the advantage of playing GBA games so it's better to keep that, especially when you still like your GBA games.

Not to mention your DSi will probably net you more money because it is newer and any DSiware you have can be transferred over to your 3DS (though you'd need to transfer it before selling it, of course).

If you're going to sell, ditch the DSi. However, waiting until Christmas is an okay choice as well, seeing as it's only 4-5 months away.

I'll just wait untill christmas!