Latios and Latias in ORAS didn't change anything. These likely won't either.
You're right, I didn't stop to consider Latias/Latios being on call. What really made me second guess the standard rules were that these pokemon seemed to be called upon by choice- but as you put it that makes it no different from the Eon Flute
I'd say about 30. They typically leave enough spaces for a living Dex and then some, so that should cover it. But don't hold your breath. Pe-XY, most of the "PC" focus went to Pokemon Bank, which we still need an info dump about (it's supposed to get a SuMo and VC update.)
That sounds about right. I got curious and actually looked up the box limits of previous generations, and was surprised by the numbers at the very end
Currently we have 31 boxes I believe in Gen 6- but I think you're still correct about it remaining at that ~30 box limit. Here are the stats:
Gen(Total Species) /
PC capacity(#boxes) / Additional spaces beyond 'Living Dex'
Gen I (151) / 240(12) / 89
Gen II (251) / 280(14) / 29
Gen III (386) / 420(14) / 34
Gen IV (493) / 540(18) / 47
Gen V (649) / 720(24) / 71
Gen VI (721) / 930(31) / 209
Gen 6's whopping 209 free spaces beyond a living pokedex is actually pretty curious. The new species introduced were also fewest on record too. Which makes me think that Generation 6 and 7 now with Sun and Moon may have both been planned with the Pokebank in mind from the start- as there is more than enough room for another generation of~130 Pokemon before the "spare space capacity" goes lower than previous generations since 1 and 2[*]. Perhaps it was simply easier to create a Pokebank ready for Gen 7 from the beginning with access to 31 game boxes to make the software more compliant and remove any problems for Gen 7's arrival later on.
With that in mind, I really do think the limit will remain at 30/31 boxes for the first time in a Pokemon generation. The Pokebank itself is always another piece of software that can be guaranteed to sell if people find their Pokemon collection cramped.
[*] exceptions to Gen 1 and 2- but the boxes and data structure was pretty different, only 20 pokemon to a box instead of 30- and the total numbers for storage actually changed between Japanese and Western releases slightly. From Gen 3 onwards- it appears the data and storage has remained relatively identical