I'm not even really a fan of Cody...always thought he was a try hard cornball but this is probably the time to pull the trigger.
This situation reminds me of the debate that went on for years at Mania every year whether they should break Taker's streak. A lot of people felt that they should wait to give it a can't miss young star to turn them into a major main eventer but the reality is WWE is terrible at creating stars, especially male babyfaces. Cody makes sense in the way Brock made sense....he's already established but beating Roman levels him up and he can use that momentum for a big main event run.
They could run it back for another year with Roman but I feel like the run/Bloodline angle has peaked. I wouldn't delay him losing just so he can reach some title reign record number that no one even knows. He's the longest reigning champ in the modern era, that's all that matters.