I am happy with the WotC wanting to get psionics right. (This is no small ambition, as the psi community is so diverse and divided.) The psi Mystic was a good start for a base psi class, and I am happy with the takeaway that Mearls and team abstracted from the feedback in the survey. More flexibility and an optional concentration. And most importantly: more reliable balance (between the extremes of underpowered or overpowered − especially a balance that avoids a volatile swinginess in either direction. The history of psionics is prone to brokenness, and it is more important than ever to rein in irregular mechanics that never balance well.
The current article is silent about any setting assumptions. All base classes need to be designed to function well in almost any setting. Personally, I feel, the psi Mystic class must be able to function within a traditional D&D fantasy setting seemlessly within the medievalesque vibe. This is easy to do with flavors of monastic mysticism and mind magic of mind-over-mind (telepathy, enchantment, charm, domination, illusion), mind-over-body (shapechange, healing, and buffing), and mind-over-matter (telekinesis = fly, invisible force damage = magical energy, explosive thunder damage = thrust, and force shields = force constructs), and mind-over-space-time (divination).
At the same time, it seems to me, a Near-Future setting is perfect to showcase the psi Mystic class. Here, the psi class can work well to convey almost every X-Men and Star Wars Jedi vibe.
I notice the current article is silent about the Far Realms setting. I hope this means an effort to make the class as setting neutral as possible.