It is arguable whether or not McCarthy has one set ending because there are many possible ends in The Road. There is the literal end which is when McCarthy finished writing but there is the end of the focalisers’ journey on the road when they reach the shore, which was their destination, or alternatively, there is the possible interpretation that the end of The Road is when the man dies as he is a focaliser. Another area of interpretation of this question is the level of pessimism as “unbearable” suggests that it is so devastating that the reader couldn't continue even if there was more to read. I personally think that yes it could be interpreted as a pessimistic end (all three aforementioned) however there is also an inevitable spark of hope as McCarthy makes sure to create more narrative gaps instead of answering previous ones.
McCarthy ends the novel with the boy being found by a man who is shown as being the only colour in the grey world the book is set in, wearing a “gray and yellow ski parka”. The reader can infer that if it is anything like the jackets we have now, the yellow in the jacket would be extremely bright and prominent in a world so void of any colour, which could be interpreted as him being a beacon of hope in such a dull world, and therefore a beacon of hope for the boy. However, I see how it is possible to see this as being pessimistic as ski jackets are known to be big to keep the warmth inside which would be an essential in the world McCarthy has created, so the reader could suppose that surely other people have tried getting it off of the man but the fact he has it could mean he has somehow avoided getting it taken, and with the previous interactions in The Road, we as readers could guess that he probably killed them to do so, making the reader believe the boy is in grave danger. But a critical view made by Adam Roberts was that The Road is