We have not had a full ultra series since 2006. Are we likely to get one any time soon? Perhaps, but it will be no Mebius if my guesses are correct. There are several reasons for this, but to properly explain we have to go back to 2004. 2004, the year of the "different" ultra series, Ultraman Nexus.
The Ultra Series was pushing on steadily, Cosmos receiving decent ratings ranging from 4-7%.Then for some reason someone decided a change was needed, and the result was Ultraman Nexus. Then followed a disaster of terrible marketing and mistaken audience, and what could have been a fairly successful show ended up turning out the lowest ratings in the franchise, Labyrinth gaining a mere 1.7 viewership. (Later, the "other" adult-oriented show, Ultraseven X, would gain lower ratings, but that was largely due to it being broadcasted at 2 am. Retsuden, a clip show, earns about that much. A clip show gets ratings which are around the same as those of Nexus).Ultra has never fully recovered from 2004. Max returned to a more tradition "scifi/mystery anthology" orientation, like the original shows, but still kept an element of the superhero genre obtained in Ace. Both Max and Mebius did fairly well, earning around 4% average, but weren't particularly good toy sellers.
Then we got Ultra Galaxy Mega Monster Battle, which REALLY boosted well in toy sales, earning countless spinoffs. Mega Monster Battle: Ultra Galaxy Legends The Movie earned nearly as much in toy sales as Mebius did in its full run. Naturally, we had Ultra Galaxy Spinoffs and a lot more Zero.
However, in Galaxy Legends we got something different. Koichi Sakamoto was added to the team, and his fame for action-based entries really showed. Before this, the Ultra Series had a lot of variety, but was generally a mystery show and less of a superhero show. In fact, Ace and Nexus were the only two to really have "big bads" and "plots" in the sense of Rider and Sentai. Sure, we have Black End and Empera and Gatanozoa, but they are hardly a physical presence from the start of their shows and only show up in the final arcs!
However, with Sakamoto we saw turn to a more traditional big-bad plot-based storyline, with Belial becoming the recurring villain in his Ultra Zero Fight, as well as the other films which were not directed by him but carried his legacy. With Ginga and Ginga S, we also have a recurring big bad, Dark Lugiel. All these shows are heavy on the effects and action scenes, Ginga not so much but Ginga S certainly so.
We have seen a shift away from the (admittedly amazing) lumbering kaiju battles of Mebius and Max. We have seen a shift away from the mystery/scifi and into full-tilt superhero genre. By superhero, I mean that the ultra series is now competing more directly with Rider and Sentai. Before it was certainly a superhero show, but it was also mystery/scifi. (For instance, the episodes Butterfly Dream, Ocean Waves of Time, Lonely Paradise, and The Dragon's Lover clearly hold more in the tone of the earlier Ultraseven/Ultra Q style.)
It's not the same. The recent entries into the Ultra Series do not have the Showa storytelling or style traditional to them, but rather follow the Sentai/Rider superhero archetype. It works, however, the franchise is making a rebound among children while catering to the older fans with tantalizing appearances of past heroes and monsters. These previous stars may be themselves, but the series is very different.
And it's working. We're likely going to see more flashy Sakamoto-style effect scenes and more of a Rider/Sentai feel in the future. We're not likely to get a Showa-style series like Mebius.
For me, that's sad. But if it's rejuvenating the franchise, I'm glad for it.