In this Wikipedia article on Arhat in Mahayana Buddhism, it is written:
Instead of aspiring for arhatship, Mahayanins are urged to instead take up the path of the bodhisattva and to not fall back to the level of arhats and śrāvakas. Therefore, it is taught that an arhat must go on to become a bodhisattva eventually. If they fail to do so in the lifetime in which they reach the attainment, they will fall into a deep samādhi of emptiness, thence to be roused and taught the bodhisattva path, presumably when ready. According to the Lotus Sutra, any true arhat will eventually accept the Mahāyāna path.
In this Wikipedia article on the Eternal Buddha, it is written:
In east-Asian Buddhism, the Buddha of the Lotus Sutra is regarded as the eternal Buddha. "The Tathagata´s Lifespan" chapter (ch 16) of the Lotus Sutra portrays the Buddha as indicating that he became awakened countless aeons ("kalpas") ago. The sutra itself, however, does not directly employ the phrase "eternal Buddha".
In China the Lotus Sutra was associated with the Mahaparinirvana Sutra, which propagates the tathagatagarbha-doctrine, and with the Awakening of Faith. The Mahaparinirvana Sutra presents the Buddha as eternal, and equates him with the Dharmakaya.
If the Arahant in Mahayana Buddhism goes into a deep samadhi after death, till he wakes up and continues the path towards Buddhahood, and if after becoming a Buddha, his personality can persist as an Eternal Buddha, then this shows eternalism in Mahayana teachings.
An Arahant who can go into deep samadhi after death (without a body) only to reanimate later implies the existence of a soul.
Furthermore, the story of Buddha Prabhutaratna from Wikipedia also has elements of eternalism:
"Great-Eloquence Bodhisattva" wants to see the Buddha in the stupa but Prabhūtaratna's vow makes it a prerequisite for showing his body that the Buddha who proclaims the Lotus teaching collects all his manifestations. At this point Shakyamuni summons from around the universe countless Buddhas who are his emanations, lifts the entire assembly into the air, and opens the stupa. Prabhūtaratna praises Shakyamuni and invites him to sit next to him. Shakyamuni then continues to preach the Dharma. In the 22nd "Entrustment" chapter of the Lotus Sutra, Prabhūtaratna and his stupa return to under the earth.
Eternalism (sāśvata-dṛṣṭi in Sanskrit) was rejected by the Buddha's original teachings on the Middle Path, as described by Ven. Dhammananda Mahathera's article (from here) excerpt below:
Why did the Buddha deny the teaching of eternalism? Because when we understand the things of this world as they truly are, we cannot find anything which is permanent or which exists forever. Things change and continue to do so according to the changing conditions on which they depend. When we analyse things into their elements or into reality, we cannot find any abiding entity, any everlasting thing. This is why the eternalist view is considered wrong or false.
My question is:
Does Mahayana Buddhism teach eternalism? If this is not the case, then what is the right interpretation of the Mahayana teachings on Arahant and the Eternal Buddha above?
In the question above, when I wrote "Mahayana Buddhism", I mean particularly in the context of the Lotus Sutra and the Mahayana Mahaparinirvana Sutra.