The handheld market is not reverting to GBA levels. I don't think some people here realize exactly how well the GBA sold. Looking it back it was an insane risk to launch the DS because no matter what they said they couldn't go back to the gba when they stop developing games for it, so they essentially killed a record breaking platform. It makes me wonder where the hell that company is at right now
Yeah, it pretty much is reverting to GBA levels. Through 9 quarters, the GBA was at 33.81M, and the 3DS is at 32.48M after 10 quarters. As pointed out,the GBA was a lot cheaper, and Ruby/Sapphire had already been released within those first 9 quarters. There are regional differences in the sales (3DS is weaker in the US, stronger elsewhere), but the worldwide numbers are similar.
In addition, for as badly as the Vita is selling, it will still do better than the NGage+Wonderswan pulled in that generation. It's still pretty much the same market overall.