Shouldn't Naruto be able to regain Kurama's chakra, and Sasuke, his Rinnegan? The following contains spoilers about recent Boruto chapters. Markdowns will still be added.

 As of Chapter 53, Boruto was controlled by Momoshiki via Kāma, then proceeds to stab Sasuke's left eye which possesses a Rinnegan in order to block him of Amenotejikara, his Space-Time ability. And also, of Chapter 55 of the Boruto manga, Kurama dies after the use of &quot;Baryon Mode&quot; which combined Naruto and Kurama's chakra.

I will be breaking this question down as to why I feel Naruto and Sasuke should be able regain these powers, starting with Naruto.
According to the wiki:

The Ten-Tailed Beast (十尾, Jūbi) is the original, primordial demon of the Naruto universe. All nine of the tailed beasts are but portions of chakra divided from the Ten-Tails.

Considering the Ten Tailed Beast (Juubi) is the combination of all nine Biju's (Tailed Beast) Chakra, this should mean logically that Kurama's chakra is the mixture of all Tailed Beasts from one to eight tails. Considering this, the Bijuu should be able to reform Kurama's chakra by mixing theirs, and give it to Naruto so he can get some Nine-Tails chakra back. Should or shouldn't this work?
Now, to the second part of the question.
According to a Reddit page I found:

Sasuke already possessed the chakra of Indra when he receives half of Hagoromo's chakra, so he is able to awaken the Rinnegan! ... Sasuke literally got Chakra from the sage of six paths thus also getting a rinnegan because you could say that he has both indra and ashura's Chakra because he has sage of six paths Chakra.

Sasuke awakened a Rinnegan because Hagoromo's Six Paths chakra synced with his left eye's EMS, thus forming a Tomoe-Rinnegan. Considering Sasuke still possesses Six Paths Chakra (as to why his Chidori is sometimes purple, he adds Six Paths Chakra to it)

 Shouldn't he be able to awaken a new Rinnegan in his left eye if he replaces it, due to the Six Paths Chakra once again syncing with his left EMS?
Well based on the above facts I could say maybe since most of the time the sharingan users are bound to control a power based on emotions. On his case, true he has the power of Six paths Chakra but when he uses the rinnegan you can witness that he needs to charge it to it's full capacity which is why you could see the Tomoe those dots represents the charged state. So I guess he can bring out the rinnegan in his left eye but will he be able to use it for that I would say it might take time.