So much wrong with this comment, and you're avatar name doesn't help it at all...

And why make a thread just to "bash" the dialogue when the game isn't even released yet?

Maybe, but if there are more than three things you can ask about then you'll need to do multiple levels of nesting - and that gets really annoying really fast. It's not even clear that nesting is even going to be a thing; so far, not a single dialogue shown has had it (not that they've shown much in the way of dialogue, which is probably wise since Bethesda knows that they're not exactly well-known for having good dialogue).

I kinda wish that things had stayed the way they were. I couldn't see Bethesda going down this road until the second they actually did. I'd prefer the old dialogue system back if I had a choice.

But am I going to condemn a system that I have never played? No. I may be unsure about this change, but Bethesda are by far the best developers around, and I put faith that they've thought things through. I am not a fan of how Bioware does things, and thus not a fan of that dialogue wheel in Mass Effect, but then Fallout 4 is much more onto the open world scale than Mass Effect ever was.

But what if the moon were made of spare ribs? Would you eat it then?

No, it's not confirmed. It is speculation that is based on the very few snippets we've seen so far. It's a reasonable conclusion, since we haven't seen anything else, but it I think everyone needs to pump the brakes here. It would be trivial to map one of the four responses to a "More..." option that branches out further, much like Bioware frequently does. We haven't seen that, but lack of evidence is not evidence of lack.

The other big worry about the dialogue - and this one I actually do agree with - is that the text blurbs may not accurately represent what your character actually says. This was a particular problem with the Witcher, where I picked a response not realizing Geralt would lay on the sarcasm and get the opposite reaction I was hoping for. Some Bioware games do this too, but their more recent ones have clear icons that indicate the type of response you're about to give. Ideally, the solution lies in between. I don't want things handed to me a la Bioware, but the voice response should expand on the snippet in an obvious way. Fallout 4 actually looks to hit the sweet spot in this regard - particularly in the Piper conversation, there's no way to mistake any of the options for other than what they are. At the same time, it doesn't tell you the outcome in advance the way a "good karma!" icon would - maybe supporting the news accidentally makes Piper suspicious of you. Probably not, but that's the example we're given.

If handled poorly, the dialogue system will be Fallout 4's Achilles heel. If handled well, it'll be even more intuitive and expressive. I don't know which of the two it'll turn out to be, but so far it at least doesn't seem worse than 3 or NV. On the voiced protagonist, I think I'll never understand why people hate it so much.

OP, modders are always going to have a lot of work to do even if the game was "perfect". Morrowind was a text-driven game with many dialogue choices and yet there was someone who thought it wasn't good enough and created a mod to add about 4-6 options more. You literally were scrolling up and down to get to all of the options. Sometimes having too much dialogue options can be unnecessary and can diminish the pace of the game.

The Witcher 3 had a good dialogue system and even though in certain cases it was simplistic with 3(even 2!), dialogue options, it didn't matter because the stories were VERY well written and voiced. This experience opened my eyes and realized that as long as the quality of the writing, the quality of the questions and answers are good, then it doesn't matter if there are few dialogue choices to choose from.

there were a select few quests that offered a level of variance - but only a handful. Majority of quests were structured in a good, evil, neutral, learn more, set up. Some quests were outright good/evil only. A glimpse of the dialogue isn't really enough to give us an accurate idea of how every single quest is going to play out. We may be surprised by some very dynamic quest lines.

Fallout 3 was actually the first Bethesda RPG where dialog was actually a means of expressing your character's personality. In all of the TES games prior, you were picking generic topics solely to receive information; you couldn't really say your character was snide, or cranky, or funny, etc. and be able to express that in the dialog for Arena through Oblivion, or even really Skyrim.

Anyway, I doubt Bethesda would arbitrary restrict themselves to "Inquisitive, Positive, Negative, and Neutral" responses for every conversation. It's a good fit for most conversations, and it doesn't just have to boil down to being curious, polite, mean, or neutral every time, but there's nothing stopping Bethesda from changing it up whenever they need to. Like, the initial dialog choices with Codsworth are denial (This isn't happening), despair (everything is dead), and hope (you're still here). The "neutral" option seems to be the one that takes the conversation in a different direction sometimes, too, and the "inquisitive" option seems to get replaced with speech checks where applicable.

And really, I don't think Fallout 3 or New Vegas ever had more than four dialog options other than multiple questions, which can easily be nested into an "I have a few questions" topic. Then if there's ever any variance based on our stats, like an intelligence check, they can have the same topic spit out a different voiced line based on our stats. I bet it would be possible to reorganize any of the dialog from the older games into this structure without having to get into anything overly cluttered.

Maybe it's not a diamond-shaped arrangement on the PC. Hopefully it's remappable, but I wouldn't be surprised if it wasn't. Don't think any of the menu controls were ever remappable in Bethesda games.