The (Unlikely) Hypothesis

We know that the next three blocks are all going to be about Ravnica and play out the storyline there, with many believing that this will mark the end of Nicol Bolas as one of the Big Bads of the Magic storyline and who knows what happens to the current crop of Planeswalkers.

Since Guilds has come out, we know what the color pairings are for Ravnica Alliance: GU, WB, UW, RB, and RG.

Here's where it gets interesting for me: RW (Boros) has a counter-based mechanic in Mentor. It's the first time that RW has had one of those that I'm aware of. There is one other guild that has always had counter based mechanics: GU (Simic). Curiously, in a block about the ten color pairings, this leaves Black out.

What if the mechanics in Guilds of Ravnica are somehow connected to the ones in Ravnica Allegiance in such a way that they help break down the "sides" that the guilds take, leaving us with four color pairings in the final Ravnica block?

In Guilds we have the following mechanical ideas:
RW counters/attacking
GB graveyard "awareness" (Golgari doesn't actually do much with the graveyard here)
UB top of library + graveyard awareness/ filtering
GW mass creatures/tokens
UR spells with a hint of graveyard awareness

That could lead to the following mechanical setups in Ravnica Allegiance:

GU counters
WB spells
UW ...
RB mass creature
GR card filter/top of library

WB caring about spells wouldn't be the first time: extort was a very popular mechanic that, while I understand won't get used again (it scales brutally in multiplayer), a variant could be used that would align it with the UR (Izzet) guild. Philosophically, it's weird but so is the mad scientist and soldier pairing of UG and WR. Besides, war makes for strange bedfellows.

So let's set aside the philosophy for a moment. With that pairing, Green is absent.

This suggests that RB (Rakdos) might align with GW for a "mob rules" effect. GW wants to overwhelm with bunches of creatures and RB is, at least on Ravnica, all about a chaotic party. This also cuts out Blue, which at its core wouldn't want anything to do with either of those guilds.

GR (Gruul) could then mesh with UB (Dimir). Philosophically, it would probably be more 'Dimir manipulates the Gruul' but if Gruul-who has never had a solid identity mechanic in my opinion-cared about what was on top of the library or top of the graveyard (library is more likely, given Red's randomness but Green does care about the graveyard so both is possible!) along the lines of Clash, that would align nicely with what Dimir is doing and leave White in the cold.

That leaves UW (Azorius) to pair with GB (Golgari) and this is the difficult one. I just don't see that guild caring about the graveyard for any reason, mechanically. Now, philosophy might be different? Azorius cares about order and the natural order of things is to die. The Golgari do not subvert the order, they are enforcers of that order.

There's one other cue and that is that Jace, a member (and possibly the leader of, now) the Azorius guild, partnered with Vraska in the Ixalan block. That is a storyline reason to match up, albeit a tenuous one on my part. I just don't know how you make it work mechanically.

But if this is accomplished, then it leaves out Red.

Here's where I'm going with all of this: I don't believe Wizards has ever done a 4 color block or set. They've done a Commander set with this-but that's it!

Woudn't this be a perfect time to do it? The mana is there, the guilds are there to support the color theme, the novelty would be epic. They haven't told us the name of the third set yet: why not? Could it give away key story or mechanical points? Maybe! It would be a good reason to hide that name.

Is this going to happen?

Oh, hell no.

But it's an interesting notion.