Zelda will still score well but reviewers get more harsh when a genre has more competition to review against or comparatively to. Zelda has never had that type of competition until now since the WItcher 3, Skyrim and Final Fantasy 15 came out. They were lucky to have been alone in their type of open world for some time, but that time is definitely over now. They most likely have added mechanics that are from newer games as well as their old ones.

I see many people (including I) expecting the game to score at least a ninety. After looking at BotW and seeing the five years of its creation, I think there will be a rather wide gap in reviews ranging from the low seventy's to close to one hundred. Here is the logic to my thinking. I have bolded the main points for convenience. 

1) Long wait

There is no point in denying this- we waited very long for this game. Delay after delay, we eventually had concerns of the Wii U's version being cancelled. Thankfully, that isn't the case, and we shall finally be able to play the game in exactly ten days.

"What the hell is your point then?" you may ask.

To establish my point, I'd like to refer to a game which was delayed for more than twice as long as Breath of the Wild- Final Fantasy XV. If you were to read many reviews and listen to opinions of gamers, a decent amount of people felt as though the wait did not compensate for the final product. With the lofty standards we typically put on the Legend of Zelda series, who is to say reviewers will not remove points for similar reasons? 

2) Lack of Wii U exclusivity 

While the majority of people do not view this as an issue (I honestly don't), I feel like there may be someone who will nitpick and lower their intial score due to this. Many people anticipated this game to be the final gem to a forgettable console, so seeing it be shared with the Switch was anticipated for two reasons- at the same time, it definitely sent the Wii U down to the center of the earth. 

At the same time, Twilight Princess was released on both the Gamecube and Wii. Is this simply a tradition from Nintendo, or did they do cross-platform releases due to the Gamecube not being successful? depending on how a reviewer may view the situation, this may change their reception of this game.

3) Poor DLC execution

Many people felt a bit disappointed when they say the season pass. While the third DLC release did have content, the first two "packs" felt like a rushed attempt to make the $20 price tag worth it. 

Will this affect me? Personally, no. Keep in mind however that reviewers may also take the DLC into consideration when playing the game. After all, it is still part of the game- it is just locked behind a paywall. They may lower their review due to the actually desired DLC (excluding the "new hard mode") will not arrive for quite some time. It would be completely justified for them to be disappointed in what will be given at the beginning.

4) Differences between Wii U and Switch

As we know, the Switch in docked mode is equivalent to approximately eighty percent of the Xbox One's power. When undocked however, it is closer to a more powerful Wii U. Does this mean the Switch will create Nintendoom? No, but the lack of an insane difference between the Wii U and Switch version will probably bring grumbles from the graphic-obsessed gamers. 

I do not condemn people who desire the highest resolution in 60fps+ gameplay. I just don't want anyone to criticize the Switch version for not bringing major improvements versus the Wii U version.

5) voice acting and open-world gameplay

We have never receiving voice acting in a Zelda game- that is, any good Zelda game (Legend of Zelda CD-i is a pure mess). We are also being introduced to open-world gameplay in the series. Add in additional new features, and we are basically departing from the traditional Zelda games we are used to. 

I anticipate some reviewers slashing off points due to it "not being an actual Zelda game". From time to time, we have always seen nostalgia and presence of change cause anger from some people. We see it from Pokemon all the time. We need Kanto back, the original starters were cool, Brock was the best waifu, etc. This constant reference to the past hinders some series due to people always pushing away change. It'd be a disappointment if Breath of the Wild was given lukewarm treatment just because it is different from other Zelda games.

Conclusion/TL;DR:

No, this isn't a "Breath of the Wild is a failure" thread- it is the opposite. It will definitely sell well, but I am concerned that we will see a lot of nitpicking from reviewers. Worst case scenario, the game gets a score around the low eighties and is still a tremendous game. Just because it does not excel ninety, that does not signify that it is trash or anything bad.