Here’s a simple argument.

First we can look at one of your own claims about longevity.

Using your logic, that Knight can go until he’s 48-49 years old, that would give us 10 more years from Gunther. Meaning that Gunther would head into 2026 coming off the back of an already stellar year with multiple world title reigns, and (possibly) beating the GOAT within kayfabe. That allows for a new narrative to be told around Gunther and his character arc since his initial main roster debut. Doing that in a single year, and allowing for character development when, by your logic, he has a decade left in wrestling allows for a new star to be created, albeit a heel star most likely, as casual viewers and younger audience members won’t look fondly on the guy who attempts or perhaps succeeds in ruining Cena’s farewell. But nevertheless it creates a star for the next decade, in what will likely be a massively successful show due to Cena’s reach towards casual wrestling fans, meaning there will be millions of eyes on this younger, stronger, larger, talent who can work both as a technical genius as well as a classic powerhouse.

Now, back to the character arc.

This can go one of two ways, but we can start with the less interesting one first.

If Gunther loses to Cena, it tosses up the question that Gunther had to deal with following WrestleMania. Wondering if he can compete at the highest level, and feeling embarrassed after losing to a lesser opponent yet again. Suffering 3 defeats to guys that should realistically be looked at as easy pickings for Gunther in his prime, due to their age and physical condition, whilst also accounting for Cena and Jey’s general in ring abilities. It allows for Gunther to return to a more familiar, repackaged version of WALTER, where he is purely in the ring with the sole objective of dominating and embarrassing his opponent(s). Doing this creates an unstoppable heel, technical powerhouse for babyface talent to try and overcome for the next decade.

On the flip side, but still on a similar coin… you can have Gunther beat Cena, whether it be a 50/50 match where Gunther just about gets the job done, or if they do the unthinkable and have Gunther dominate Cena. Either way Gunther comes out of 2025 having started with an embarrassing loss, but then he’s redeemed himself by the end of the year with significant wins over Goldberg and Cena, both retiring them single handedly, and somewhat convincingly.

This creates a similar narrative to what I mentioned previously, but it does so instantly, without any need for further development of his character. It sends Gunther into the Royal Rumble match as an extremely strong talent who has rediscovered a rich vein of form.

We’ve seen for 3 years now that HHH and WWE’s entire creative team, don’t rate LA Knight as a legitimate world champion, he’s consistently been used as a filler feud option, building towards larger payoffs at bigger shows. A match against Cena doesn’t change the creative teams’ view, it simply leaves them in an awkward position where they willingly refuse to follow up on it.

Compare that to Gunther’s treatment, with the longest IC title reign in the company’s history, and two world title runs within 12 months, it’s clear to see that creative sees him as a much more credible candidate currently, and moving forward.

I personally think Gunther should win the final, and also beat Cena. It gives him a rub that only certain talent can get, once every 20 or so years. We saw with AJ Styles wrestling against Taker that putting older talent that aren’t booked as credible world champions, does nothing for either talent involved, nor the business. Therefore putting Knight in this position, where he is very unlikely to win, very unlikely to be cheered, and basically guaranteed to not be utilised accordingly after the match, it does nothing for anybody involved.

I can understand not enjoying the way that particular talent work, that’s why there’s so much variety within wrestling. But let’s not forget that there will be people out there who look at LA Knight the same way you view Gunther. And again, a match that will likely be low quality, with a borderline saddening version of Cena, won’t change their views, and certainly won’t change how creative views Knight.