Epic is obviously well prepared for this. Everything was ready, the lawsuits are already out, the 1984 trailer, even a good hashtag for twitter is in place. But is it enough to defeat Apple? doubtful, especially because it's not just EG vs Apple, but basically EG against every major corporation. It's already against Google, but also against MS with Xbox live and Sony with the PS Store.
Keep in mind, Sony wants to sell the disc-free PS5 Digital Edition. Players have to buy the games in the PS Store. There's no other way. For the customers that's gonna be a pricey experience. Not only are the games often more expensive than store bought discs, Sony also gets to keep the entire revenue. If EG were to win against Apple and every publisher could use his own stores and payment methodes, this would bring down the PS Store, a very lucrative business model Sony absolutely wants.
Now this is where things get complicated, since Sony is now one of the shareholders of EG. I doubt Sony is happy with their fight against centralised app stores. Quite the opposite, Sony will not support EG, neither will MIcrosoft and the part of the development circles who are tightly connected to those corporations.
So far only Spotify sided with EG, allegedly maybe also Sonos. That's not a strong front against Apple. Basically EG can only hope for the FTC (?) to side with them, that's what their lawsuits are for, but until that's done many Fortnite seasons will have passed.
On whose side the customer will be is down to personal preference. Whoever favors security basically has to root for Apple, since one controlled and centralized store is still the smallest window for malware. Whoever is hoping for less expensive products will probably side with EG. 30% is a lot of money and EG only asks 12%. The only compromise is reducing those 30%. No matter what, MS Apple Google or Sony will not give up on having all the money moving through their stores.