I think a lot of it has to do with who you have around him. If he is 1 of 3 high quality scorers (with Fultz & Hayward/Griffin, for example), then I think it is worth it to pay him the max. Then he and Horford have their max contracts expire right around the time Fultz and next year's #1 are up for an extension. To me, that is pretty close to a best case scenario.
If things go poorly in both the lottery and in free agency and Bradley is still the 2nd best player on the team, then I think you have no choice but to make major changes. Paying big money to essentially keep this same roster for 4 more years would not be productive.
Should we be fortunate in one or the other - only Fultz or only a high level free agent, then it becomes a tougher question, and I still expect that such a roster would not be able to compete for a title.