There are a lot of talks about the vaccine that keeps on changing the number all the time, I have heard as close as 3 months and as further as 3 years, it is silly to think that we have literally zero clue about when we will have a vaccine. However I think it will not be 3 years, I do not think it will be 18 months neither, I think it will be before 2020 ends.
I know that normally these vaccines takes up time and that is why projected times are longer than we hoped for, however these projections are considering this vaccine is like any other vaccine scientists develops, which is why it is said it could take 18 months, however reality is this is a global pandemic so there are thousands maybe millions of scientists who are working on it all around the world, I think we could have it closer, which means NBA could return back to normal next season hopefully.
We still don't know how long the scientist can find a cure to this virus, although like you said, scientist are already working on it and considering 4 drugs already:
Scientists have suggested dozens of existing compounds for testing, but WHO is focusing on what it says are the four most promising therapies: an experimental antiviral compound called remdesivir; the malaria medications chloroquine and hydroxychloroquine; a combination of two HIV drugs, lopinavir and ritonavir; and that same combination plus interferon-beta, an immune system messenger that can help cripple viruses. Some data on their use in COVID-19 patients have already emerged—the HIV combo failed in a small study in China—but WHO believes a large trial with a greater variety of patients is warranted.
https://www.sciencemag.org/news/2020/03/who-launches-global-megatrial-four-most-promising-coronavirus-treatmentsBut as what @harizen said, next year should be the right term here. If everything settles down, then probably they can complete the rest of this season next year and then re adjust the calendar year for the upcoming season.