Here's a list of certain Chinese fighter jets with the year of their first flight.
Generational descriptions are, of course, quite subjective.
J6 - 1958 (1.5 gen?)
6 years pass before
J7 - 1966 (2nd gen, license built)
J8 - 1969 (early variant)
7-10 years pass before
J7A - 1976 (2nd gen, domestic)
8 years pass before
J8B - 1984 (2.5nd gen?, reworked variant)
JH7 - 1988 (3rd gen strike plane)
10-14 years pass before
J10 - 1998 (4th gen)
13 years pass before
J20 - 2011 (5th gen)
at least 13-14 years pass before
JXX - (6th gen?)
So... right now we're basically at a point where the time elapsed between two different generation of jets is the longest it has ever been.
And since the rumor mill is fairly still on next gen fighter jets, it's plausible there'll be at least a few more years until we see any such jet.
J-35/31 certainly don't count as next gen jets as they're basically the same gen as the J-20. Same reason why J-11 family wasn't mentioned at all, as it doesn't represent a new generation of jets build domestically for China.
Of course, the reasons for this gap are fairly known and logical. No one has 6th gen yet. Before, China was always catching up. Now it's near the forefront. Now it's harder and it takes time to make large leaps.
And, who knows, maybe we'll see some sort of 5.5 gen plane in the late 2020s, before we see a true next gen design. Who even knows what a next gen is?
Even if it takes a 25 year gap, and if China's 6th gen flies in 2035, that might still be less than the gap observed in the USAF. 1997 for F-22's first flight (YF prototype not being relevant) and probably not earlier than late 2020s for 6th gen. That's gonna be 30+ years.