Considering how loved he is by the UFC brass, I'm sure that his legacy will be protected. Zuffa loves to prop up their company men.
In terms of how I see his legacy, I think he was great for his time and deserved to be in the p4p discussion when he was the first simultaneous LHW and HW champ, and the first double-champ to defend both belts. That was special to watch, and not a feat that will be easily replicated in the future.
That said, I don't think he'll be thought of as an all-time GOAT. Whether it's fair or not, he'll always be remembered for his two losses to Jones. Also, with the exception of Gustaffson and Rumble, his LHW resume is very thin. He beat a middle-aged 185er and a barista on his way to the title.
As for heavyweight, different story. I think there's an argument for DC to be considered the best HW of all time. His resume at that division is stellar, and it took Father Time catching up to him before he suffered his first loss at the division. Sadly, because he spent so much time trying to win at 205lbs, he lost out on the chance to stack Ws at 265lbs.