No, there's nothing at stake. PDS are going to do what they do anyway. They aren't waiting on tenterhooks to see what way this thread turns out.
You have been strongly belabouring the idea that simply becauase victory conditions exist the AI will have to be crappy and not be good for endless mode. This is not, in fact, an issue about victory conditions. It's about poor AI. And that's ok. We should all be worried about the AI. Big part of the game, right? But that doesn't explain why victory conditions shouldn't appear. The two are, in fact, unrelated. It's saying that if we don't get Endless as the core mode then Endless can't be good as an additional mode when there's no reason to believe that's so. The way to solve this is to make a better AI not to change the whole game on the off chance that PDS are crapwits with no development skills only capable of making one good game mode.
In abstract there is no better way to play between the two game modes. Again, for perhaps the tenth time, I want the endless mode. I do. I think that is the 'real' experience that 4X games have to offer. That is how I typically enjoy playing 4X games once I've learned the systems. So we are not talking at all about which of these is better. We're talking about which mode should be the first one presented to a new player. This maybe isn't the be all and end all of a games success but it is important and it does need to be hedged towards new players and to give fixed goals that help people learn and reward achievements that (to them) may or may not actually seem rewarding.
Remember; they are new players. They don't know how to set themselves goals in this world. They don't know what's possible or even plausible. And that's why they need a more closed, guided experience as their first point of contact. So they can look at the victory conditions and see what the game defines as success. It gives players a reason to look at systems they otherwise might just ignore because the game says 'Hey you can win through commerce'. That's how you take the emphasis off warfare.
In an open endless game everything always comes down to fighting. That's just the way it works. Eventually you (or someone) is going to run out of room to expand and look towards you. And this is a PDS game. The AI won't be shy about starting wars even on easy. An infinite timeline makes it certain that warfare has to be the defining factor. At least with victory conditions it ensures that other approaches are actually placed on the same level as war. Yes, it is gamey. But at least that means you can grab a win while the militant empires are too busy fighting each other to actually win the game. It rewards you for being smart and particularly as a new player it's really REALLY important to make players feel clever.
In infinite game how is playing a peaceful race of traders even plausible? All the resources are going to be taken. There has to be scarcity and so has to be conflict. And if you haven't been keeping pace with the size of your forces and your military tech then boy are you just the most tempting target.
You say you don't just want warfare, then what you are really looking for is a game mode where the resources won't necessarily all be used up, where there is enough space for everyone, at least for long enough for the victory conditions to show up. Running out of space and resources guarantees war is the only answer. No matter how peaceful you as a player want to be, a good, rational AI (that you're so concerned about) will figure out that you are an easy target.