There is no Spectrobes 3. The series concluded with three titles:
No official announcements, trademarks, or credible leaks suggest a continuation. Disney Interactive (publisher) closed in 2016. The IP is dormant.
If you want more Spectrobes, replay Origins on Wii (or via Dolphin emulator) or revisit the DS titles. The franchise's blend of fossil excavation, creature raising, and real-time combat remains unique.