Just a little while longer. We've been waiting since July. It'll all be worth it!
Do you think the line is dead after Majin Buu? :/
No, I don't think so. I hope not, at least.
Super Saiyan 3 Goku and Super Saiyan Trunks were in 2015, Super Saiyan Vegeta 2016, and Super Saiyan 4 Goku and Super Buu for 2017. So it may be awhile before they announce the next release but maybe they'll have a prototype reveal at SDCC or even during their World Tour.
I'm going to the event in New York City at the end of the month and one of my questions will be where the future of this and the Figuarts Zero line are heading. We haven't seen a release from the regular Figuarts Zero for awhile.