My guess as to why Bandai America isn't really focusing too much on Tamagotchi as of right now, is because of the upcoming Power Rangers Megaforce toyline. It seems that a lot of their effort is going towards that, and it does make sense considering it is the 20th anniversary for Power Rangers.
But still, in my book it isn't wise to leave the other stuff (Such as Tamagotchi in this case) untouched, because then people could lose interest and there won't be the market for those products anymore.
I can say that even if Bandai America has left Tamagotchi for the time being, we're not too far off from a new Digimon toyline as there is a new Digimon TV show coming in 2013, so I'm still hopeful that they'll do something. After all, Digimon partially spawned from the popularity of Tamagotchi... ^_^