Title question asked by OP on Jan 14 at 11:42 ~
In Mahayana Buddhism, do they expect everyone to become a Buddha? If so how can any Buddha help anyone to attain enlightenment?
Yes. For the 1st question.
I do not understand in logic, how the following 2nd question had to be asked. Explanation - by replacing terminologies with daily words:
In Medical Science (Mahayana Buddhism), do they expect everyone to become a healthy person (Buddha)? If so how can any Medical Scientist (Buddha) help anyone to gain (attain) health (enlightenment)?
In this replacing terminology practice - purposefully making it easy for OP used doctor-patient analogy, cannot one see the burble of asking the 2nd question? Or, it's still too hard to grasp once the healthy person replaced by medical scientist? Are scientists not persons, or a person not scientist? ...Maybe need more learning on Logic and Sets then.
Question content elaborated by OP on Jan 14 at 11:42 ~
In Mahayana Buddhism, do they expect everyone to become a Buddha? If
so, how can any Buddha help anyone attain enlightenment? Isn't the
whole point of becoming a Buddha to help others to attain
This the same as title question, intriguing to read; yet to utilize what asked, enlightenment for human beings is a gradual process. 2500 years after the Buddha entered Nirvana, there are 7.442 billion (2016), only maybe a fraction as small as paramāṇu (micro-dust) enlightened, plenty works to do. The OP seems worried there not enough unenlightened persons left to let the Buddha enlighten them :).
It's like asking everyone in the country to become kings. Then there
won't be any countrymen left to rule.
This is not a legitimate analogy. Countrymen vs Kings, ruler vs ruled... this is a Samsaric formula, which Buddhism, the pinnacle of Buddhism, dedicated to transform. For the Buddhist ideal, there no kings, neither ruled; everyone is his own king, his own master; not mastered by Mara, or other, or society, or greed/anger/delusion, or any mental affliction... etc.
To give another analogy, imagine patients refusing to follow doctor
advice saying that they want to become doctors first to help cure
others. Then those future patients they are hoping to help would also
have to refuse their help to try to become doctors themselves. At the
end of the day, no patient makes use of any doctor and no doctor cures
any patient. So why become a doctor in the first place?:)
Again it's amusing to instance patient refusing doctor advice by claiming himself doctor to cure other first (??? / I commented, but being moved to chat). A patient aspired to be doctor doesn't make him a patient refused doctor advice, unless his mentally afflicted; a doctor can be sick so he a patient, a patient can be cured and then learning medication became the doctor... etc. etc.
The heart of Mahayana Buddhism is to aspire to become the Buddha, for that the realization greatest potentiality of any sentient being, especially Human Being. To be a Buddha is to regain the totality of one's beingness without defilement (but of course there more profound teachings about defilement is not defiled for what originally perfect can never be scathed). As a Buddha, naturally he will aspire for the greatest benefit of all sentient beings, the greatest most wondrous existence is being a Buddha - so a Buddha will help all sentient beings to attain Buddha-hood. Buddha = compassion = selfless love, just generalization; the mind of the Buddha is beyond comprehension, it said.
To produce a Buddha, the "everyone" (unenlightened beings) is the ingredient. Through helping others to attain liberation, a Buddha is born. Said in 《普賢行願品》 (The Aspiration of Bodhisattva Samantabhadra) that this whole is like the Bodhi tree, the leaves and branches the sentient beings, the root Prajna-paramita, the fruit the Buddha. Without any one part, that's not a tree any more. Help others attaining liberation from simply ridding illness (many real Buddhist practitioners possessed this healing power naturally), be their trustworthy friends, providing services, giving virtuous advice... to enlighten them, all go gradually or spontaneously.
Like, if you real wealthy, that must be when you can give to anyone in need; you a kind person, that must be when you showing your kindness to others; you good doctor, when have cured a patient with terminal illness. Likewise a Buddha a Buddha is by helping sentient attaining enlightenment.
There will always sentient beings be born into Samsara, for Samsara denoted cyclical recurring. Unless all sentient awake all at once in this Great Dream of Maya. Obviously from the beginning-less and endless of spatial/temporal dimension, this never happened, else we won't exist (are we the dream dreaming our existences or we dreaming the dream?? - Zhuang Zhou and his butterfly metaphor :). For the fact this never happened, I can surely infer it will never happen too, simply, Samsaric time is beginning-less and endless (I know many won't be able to understand at here - I will be misunderstood, again!!). So those who don't understand Mahayana will intercept here laden their lethal attack - liberation of all sentient beings a futile aspiration!!
Yes, futile; but that almost ensured there will be plenty of unenlightened sentient to be liberated (solved the OP's intrigue ;). It ensures anyone aspired to be the Buddha will have plenty and more than enough ingredient to work on :). Further, a futile attempt doesn't diminish the one who held the greatest aspiration - in fact the glorious of such spirit. Isn't there a popular gig: Impossible = I'm possible :)?
It could go on and on... to cut short and conclude, the enigmatic Mahayanists proclaim,
眾生無邊誓願度；(innumerable sentient I vow to ferry across)
煩惱無盡誓願斷；(endless fetters I vow to cut off)
法門無量誓願學；(countless Dharma gates I vow to study)
佛道無上誓願成。(unsurpassable Buddha Path I vow to accomplish)
These original Chinese Mahayanists are likely, crazy. Yeah.
Do not confuse the Chinese Mahayana Bodhisattva Samantabhadra with Tibetan Samantabhadra. Chinese one the handsome young man with beautiful clothes and adornments riding on white elephant; whilst Tibetan is blue-skin naked in copulating with his mate.
Chinese Mahayana Samantabhadra