Honestly, it might go away, but with all the diseases and allergies that the people of this world have, including myself. I've had my cat for 10 years, and I still can't get close up to him because my allergies drive me wild; Tamagotchi is bound to stick around, or come back better than ever, due to the fact it still teaches responsibility, it still makes you fall in love with those that care enough to get involved, and it still gives those that are allergic, or bed-ridden, etc, etc, a chance to care for a pet. Yes, it's digital, but it's also portable, so things like NeoPets, Adoptme.com, etc can't compare.
yes, it might die out a bit, because there are so many things that pop up every day that take more time, and more focus to complete, or just to take part in, but for those that want something that can be cared for, and truly love you unconditionally, I think we're good.
Personally, and PLEASE DON'T TAKE OFFENCE TO THIS - I think anyone from the ages of 13-25 who want to have children, should be gifted (or demanded) to raise and take care of a Tamagotchi, for exactly 3-6 months. Including job, parties, etc.
I don't have a child, but I have been babysitting for friends and family since I was 9. Children are just as easy and difficult to look after and take care of as Tamagotchi are. Dead serious.
So... hahaha, yeah... They may even come back as a birth control method... >.>