You're making a big deal over literally nothing since there isn't even any remote hint of delay in the other two titles whatsoever at this point in time.
Like I said, I could be wrong, but you never know. None of us really have an idea what's really going on with Square unless we go and work there ourselves. *Shrugs*
No, we have PLENTY of idea of what goes on at SE without working there: Right now they're making those three things and releasing them when they're currently slotted to be released.
They released all their previous DLC on time, and the one that involves a completely new thing: online multiplayer. That was delayed for what was ultimately two weeks (typically about one Sprint for most software dev teams). This is because if you're looking at improving launch stability for online play, that's 100% the most critical time for new/returning players to form an opinion of it, and it's dealing with complexities that nothing else they've made for the game has done so far, so a small delay to tighten that up is completely the right move.
That's ZERO basis to go making claims that everything else that they're working on are going to be delayed from this, but they're just not talking about it – ESPECIALLY since the Episode Ignis trailer that contained its release date
was shown 10 days AFTER the Comrades delay was announced. If there were going to be KNOWN delays because of release date proximity concerns, they would've been addressed all at once, and especially before showing off Monster of the Deep & Ignis again with release dates attached.
This self-admittedly crazy claim has just as much merit as – if Monster of the Deep underperformed slightly in sales when it releases – that they'd cancel Episode Ignis due to overall disinterest in FFXV, backed up because, "none of us REALLY knows what goes on without working there."
Until there's actual EVIDENCE of something affecting the other DLC, don't go to extreme conclusion jumping over Comrades postponing their launch.
EDIT: Also, the Monster of the Deep preorder is $29.99, so there's no need to speculate on it being potentially prohibitively pricey (especially since having the PSVR to be able to play it at all is already its own barrier of entry).