Oh, no, PLAAF to buy J-35/XY has always make sense to me, or least there are always some tiny little chances for that to happen. In fact PLAAF has history of bought aircrafts it really don't want (certain J-7 and J-8) and bought something it later proven useful by PLANAF (JH-7), so of course, there is a chance for PLAAF to buy some J-35/XY in the future.
But, I consider that chance as very slim and far from getting any conclusion, or too much speculation over the latest rumors in the pass few years.
1. it remind me too much of netizen fight story over FC-31, carrier based 5th fighter, and even J-20 on and off
2. logically, as you mentioned, even if landbase J-35/XY project goes smoothly and start mass production in late 20s or early 30s, why can't China invest more on 6th gen fighter, which could out in 2030~2035? and most of all, what happened if SAC win the 6th gen fighter procument??? SAC is going to produce two very new 5th gen and 6th gen fighter at the same time from mid 2030s?
in fact, at this stage, with 6th gen fighter competation in few years, shouldn't SAC focus more and 6th gen fighter instead of a landbase J-35/XY, after all, it took FC-31 almost 10 years to get the oppertunity after SAC lost the competation.
3. none of current rumors are 'straightforward' enough, what I mean is, given 'landbase J-35/XY' is still a rumor and not 100% concret, the rumor of 'PLAAF to buy landbase J-35/XY' or even 'to buy a lot landbase J-35/XY' just another step ahead. There is also a very good chance that after 'landbase J-35/XY', PLAAF still find no interest, and it's a practical a FC-31 V4.0 or somthing like that, could be SAC's F-18 to CF-188
So, of course, it's make sense for PLAAF to buy J-35/XY, but at this stage, it's too early to discuss what kind of impact will it make to PLAAF, just like discussion over what if PLAAF bought FC-31 V1.0 or V2.0