Problem is that the MCU is very much a "high-risk/high-reward" franchise where just one single movie even merely under-performing can hurt the franchise (see Disney's Star Wars trilogy) while a true and honest box office bomb can outright kill the franchise and by extension, possibly the entire capeshit movie genre for the foreseeable future.Nah, as long as Marvel has enough profit on their movie division, they're going to have more than enough spare change to sustain the living corpse of their comics division.
The MCU has already reached its peak with Endgame, which was meant as the "grand finale" of the MCU when it first began and the Spider-Man movie they did was probably just a quick epilogue meant as a thank you to the fans. Due to some weird contract issues, X-Men can't get into the MCU for a while despite Disney's buyout of Fox and there's the unexpected factor of COVID-19 and how Disney in particular was hit hard by it.
Now Disney is scraping the bottom of the barrel for the fourth phase of the franchise since most of the old cast is gone and they can't feasibly bring in X-Men or Fantastic Four until the mid-2020's. They're bringing in "literally who?" tier characters that make the Guardians of the Galaxy from back in the 70's look like A-Listers as well as universally reviled "Woke Marvel" characters like Lady Thor and possibly even America Chavez.
The normies who provided the backbone of the MCU's success mainly tuned in to see how it would all play out with the big Infinity War/Endgame finale and they got it. Plus, COVID-19 has likely given those same normies more time to detox off the capeshit
The only movies announced for Phase 4 that I think will be guaranteed successes are the Black Widow prequel since she is a beloved character and this is apparently Scarlett Johanson's final role in the MCU (I get the feeling it was probably meant as a late Phase 3 film but got delayed) and Doctor Strange 2 since he's a well-liked character and Sam Raimi is supposedly going to direct it.
Anything after Black Widow and Doctor Strange 2 is in the running for being "the big one" that flops at the box office and kills the MCU, especially if it happens before they can officially get the X-Men into the franchise.
If the MCU crashes and burns, the mainline American comics industry dies with it.
At best, you'll see Disney and Warner keep Marvel and DC around as IP holding firms and to sell reprints of older titles and issues still popular with fans, essentially it'll be the usual omnibus editions you see for sale on Amazon and at Barnes & Noble.