There are two main aspects: need and value. Many people, both hearing and deaf, see a need for deaf community, Deaf Culture, and ASL, but I'm not certain they see a value in it. Some, both hearing and deaf see neither need nor value, and a few, such as The Alexander Graham Bell Association for the Deaf and Hard of Hearing , see it as blocking progress.
I believe Deaf Culture and ASL will exist in some form for as long as people see value in it, whether there is a need or not. In some far distent science fiction future it might be a group of all hearing people who get together once a week and communicate with nothing but sign.
Let us look at the proven value of Deaf Culture and ASL.
It has been said that deafness is the only disability that brings those who have it together, and in this it is unique. By the very nature of this 'bringing together" it has put deaf people at the forefront of any discussion, legislation, or action concerning people with disabilities. When it comes to challenging societies definitions and preconceptions of what disability is -- Deaf are the leaders.
This is a value to society as a whole: It needs this challenge to keep it from stagnating in its own all powerful ignorance.
ASL has contributed to linguistics and therefore our knowledge of humanity and language by its very existence. While in no way lessening Stokoe's contribution it is a fact that a thousand Stokoe's could not have made the cultural impact he did if ASL or its equivalent had not existed. And as long as ASL did exist someone, if not Stokoe, was going to discover and prove it as a unique language.
Without Deaf Culture it is unlikely ASL would exist as the highly developed language it is.
Would society be poorer if Deaf Culture did not exist?
You better believe it.