Pretty straight forward here... Do people actually want to see these lists get expanded? The polymorph spell is pretty much good forever with it's rules. Creature companions basically require your GM to do all the heavy lifting if you aren't using a prebuilt, but could technically be considered future proof (though it'd be nice to see more printed).
The description for AA4 leads me to believe the appendix space in the end will be dedicated to building your own races this time, which seems future proof as is. Now that leaves the summon line, restricted to the few creatures in AA1 and the graft system provided. Sadly, this sure seems very easy to expand, just add a line in the descriptive text stating this can be summoned using summon creature X, then toss a small table at the end of book to really drive it home.
Obviously a new summoning graft would take up a fair bit more space, but a few more of those could be fun since it'd be nice to see a summon or 2 with more unique abilities like a spell like or something of that nature.
At the very least, is there any intent to ever expand these lists since there's now 2 full books with a 3rd coming and nothing new in years now? Do other people want to see these lists expanded?
I'm all for seeing new grafts for summon monster. It's not hard to make them yourself, but some more in APs or a sidebar in alien archives for certain entries would be appreciated. I'm less enthused about adding unique creatures to the lists.
Summon monster was problematic in pathfinder because of all the unique creatures on the list. A monster on the ninth level list was basically 'summon level 14 cleric', or the level 6 'summon level 7 bard' (IIRC). I'd rather those options were thought about more in advance.
Some more grafts would definitely be appreciated, as would any way to make two summoned creatures of the same graft not 100% mechanically identical. It's abit dull for literally every summoned demon to be same for example and that inevitables always use the exact same weaponry.
Yeah, what Milo said is basically why would want a few more uniques. But I certainly understand the hesitation given the summon options of PF. That said, a few more uniques could add some more variety. Or even a couple grafts you could apply at the end to tweak the summon possibly. I'm not sure how it'd work, but something geared towards the creature "arrays" you tack on at the end. Raises this but lowers that type thing for a net neutral change to add some uniqueness to the generic options.