According to latest posts date in this topic, quite a long time ago 
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Today I was looking for a Rasa roadmap too.
Still could not find one.
I’m interested in, amongst others, :
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Lifecycle of versions; f.e. when will 2.x be depricated and when is 4.x to be expected.
What’s aimed to be in 4.x -
Major changes like data format; f.e. we’ve had md-> yml; also the slot mappings from form to slot sector.
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Roadmap related to the five levels of CA.
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New features growing stable. F.e. and especially
end-to-end training, and even more specificly when will it be incorperated in Rasa x 
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A roadmap helps us with planning and deciding.