Yes, if the Monomachine is the first, the Octatrack should surely follow!
Elektron’s machines up until this point pretty much satisfy a specific need pretty neatly:
Digital drums - Machinedrum
Analog drums - Rytm
Digital melodies - Monomachine
Analog melodies - Analog Four
Inevitably you’d want some flexible sampling, and so the Octatrack fills that gap.
Elektron have got it nailed from this (perhaps pigeon-holed) stand-point.
Having said that, they all cross over between purposes - the Machinedrum will do mad melodic sounds, and the Analog Four will do seriously awesome drums.
Perhaps I’ll stop talking before getting into crazy fan-boy territory - whichever you end up getting, you won’t regret it.