I have a question that I find kind of interesting, and can't find an answer anywhere. Will the next Buddha find a new path, different from the middle way? Or will he rediscover the middle way once it's been forgotten. I think both are possible, but I'm not too sure.
Each Buddha rediscovers the same path and the same truth all over again, on his own.
You can find this narrated in the Pali Canon for Vipassi Buddha (SN 12.4), Sikhi Buddha (SN 12.5), Vessabhu Buddha (SN 12.6), Kakusandha Buddha (SN 12.7), Konagamana Buddha (SN 12.8), Kassapa Buddha (SN 12.9) and of course, Gotama Buddha (SN 12.10).
Furthermore, the Buddha foretold the coming of the future Buddha, Metteyya Buddha or Maitreya Buddha in DN 26 - to do the same.
When someone awakens (Buddh) he or she awakens to the Key Principle. This Principle is at the root of everything. This Principle is the Law of Nature. From this Principle everything else follows, good and bad. If you know the Principle, you can act accordingly and fare well. If you act otherwise, you create trouble.
When the Awakened awakens, he or she teaches the aspects of the Principle as well as the implications of the Principle. He or she teaches the different outcomes of Acting in accordance with -- or against -- the Principle.
To those who want to fare well, he or she teaches the practical means of mastering the Principle. Sentient beings of extremely high capacity only need the Principle itself explained - then they can see and do the rest by themselves. To sentient beings of low capacity he or she teaches basic Action in accordance with the Principle without trying to get them to understand the Principle itself.
Sentient beings of intermediate capacity need detailed step by step instructions on mastering the Principle. These step by step instructions can take many forms. In case of the previous Buddha they took the form of the Middle Way. Regardless of the exact form they take they are a gradual approach to mastering the Principle. They come out of the Principle, their essence is the Principle.
These gradual instructions can use an entirely different set of concepts, and their practical side may look vastly different because of a different lifestyle of the sentient beings at the time. They may not resemble the Middle Way at all, but their essence will be the same nevertheless.
It will always have: this is right, this is not right, this will get you in trouble, this will get you out of trouble, this is what you need to know, this is what you need to do, this is the coarse approximation of The Principle, this is the more refined, this is extremely refined, this is sublime, these are the pointers to the ultimate.
Walking towards emptiness we walk separately simply because there are different bodies, but:
MN121:13.1: Whatever ascetics and brahmins enter and remain in the pure, ultimate, supreme emptiness—whether in the past, future, or present—all of them enter and remain in this same pure, ultimate, supreme emptiness.
MN121:13.4: So, Ānanda, you should train like this: ‘We will enter and remain in the pure, ultimate, supreme emptiness.’
MN121:13.5: That’s how you should train.”
Also, in MN81, the Buddha discusses his own experience with a previous Buddha.
MN81:5.1: “Once upon a time, Ānanda, there was a market town in this spot named Vebhaliṅga. It was successful and prosperous and full of people. And Kassapa, a blessed one, a perfected one, a fully awakened Buddha, lived supported by Vebhaliṅga.
All Noble Paths converge.
New Buddha will bring understanding to what has already been said. Majority of people are not interested in Dhamma because they fail to understand it and get lost in the myriad of books and ideas. Grasping the Dhamma is the most difficult thing to do and even more difficult is applying it in your daily life. New Buddha will do all that as the previous Buddhas did. Buddha brings understanding like a master teacher. Buddha is the teacher of Gods.