Yes, that was exactly how I read it-- Might there be any new 76-key models (similar in width to Genos and PSR-EW) coming out in the first half of 2019, possibly to be announced at Winter 2019 NAMM, but costing no more than perhaps a third or fourth the price of the Genos.
The only thing we know for sure is that only Yamaha knows for sure, and Yamaha will wait until the opening day of NAMM, or perhaps the day before, to post a press release announcing what they'll be exhibiting at NAMM.
The PSR-E models have been updated like clockwork every two years since they were introduced-- the 400-level models in even-numbered years, and 200- and 300-level models in odd-numbered years. As I understand it, the 200- and 300-level PSR-Es are big sellers for Yamaha, so I feel fairly confident that we'll be seeing the new PSR-E273 and PSR-E373 very soon, either at Winter 2019 NAMM or at MusikMesse 2019-- assuming Yamaha is planning to continue those two lines and not rename them to something else (after all, the model numbers are pretty close to running out-- 273/373, 283/383, and then 293/393). And we can therefore expect to see the new 76-key model, or PSR-EW310.
But we'll just have to wait patiently to see whether any sort of 76-key PSR-S models are coming. The PSR-S775 and PSR-S975 are still comparatively new, so I'm doubtful we'll see replacements for them anytime soon, although that doesn't rule out the possibility of 76-key versions (PSR-SW?). And there was no PSR-S675 released alongside the 775 and 975, so perhaps Yamaha will release one in 2019?
It can be fun to speculate, but only Yamaha knows for sure!