IIRC, and I was but a lad at the time, but the Benny Hill Show’s ratings took a dive in the late 80s, partially because of the Alternative Comic brigade lambasting the show as being anachronistic but also because it was becoming the same old tat every week. Sketch shows were evolving with people like Fry & Laurie + French & Saunders being more invective, insightful and satirical. Besides these fresher performers, Benny did seem out of place.
For his show to have lasted, he would have had to evolve his style. Perhaps he could revisit his 1970s musical roots and developed a more cabaret type show. The gap in the zaniness market allowed the BBC to heavily promote Noel Edmonds (particularly after they lost Kenny Everett to AIDS) and his particular brand of whackiness with the Late, Late Breakfast Show, the Saturday Roadshow and finally House Party.
What the outcome would have been is harder to call. He might have had more influence on more modern comediennes, he might have had a career renaissance like Frankie Howerd before his death. In fact, he could have lived longer as he refused to lose weight in order to carry on living. If he had more to shoot for, he could have accepted medical advice and gone another decade.