I suspect you will need Kontakt 6 when someone puts out a library that you have to have that requires the full version of Kontakt 6..
Are we seeing something similar to Serum?
Depends on what exactly you mean. You cannot create your wavetables in Kontakt like you can in Serum. But you can definitely load wavetables generated by Serum.
It's more similar to Massive, with more phase distortion modes than Massive.
I'll buy it for myself and also buy a copy for someone else on a tight budget just as soon as NI returns to a system that allows for offline activation.