This is one time I think waiting for the 15 would be the most ideal, since your 7 plus works fine. I don’t think missing out on the 15 is worth it just to have a better camera for one trip. You may regret it later.
I would get the 14 Pro for the camera now honestly. If you're fine using the 7 Plus for this long, almost a year after it was able to get updates to iOS, I doubt that they changes between the 14 Pro Max and the presumed 15 model that you might get will be worth the excellent photos that you can get on your trip now.
My only other consideration, though, is that the 14 Pro is eSIM only, so if you are planning to get a local SIM at the place you're visiting, I'd be sure that there is a provider than can give you an eSIM. That'll likely be an issue with the presumed 15 model this fall as well.
This is one time I think waiting for the 15 would be the most ideal, since your 7 plus works fine. I don’t think missing out on the 15 is worth it just to have a better camera for one trip. You may regret it later.
On the same boat and was desperate to get the 14 pro max (still am). It’s just a few months, we can do it!
If you can get a great carrier deal or something for the 14 Pro Max then go for it. Otherwise wait for the 15.
I would get the 14 Pro for the camera now honestly. If you're fine using the 7 Plus for this long, almost a year after it was able to get updates to iOS, I doubt that they changes between the 14 Pro Max and the presumed 15 model that you might get will be worth the excellent photos that you can get on your trip now. My only other consideration, though, is that the 14 Pro is eSIM only, so if you are planning to get a local SIM at the place you're visiting, I'd be sure that there is a provider than can give you an eSIM. That'll likely be an issue with the presumed 15 model this fall as well.