One thing that supports signing both whales is if the players demand a bigger share of the revenue pie in the next CBA (which they should), then it's possible that we see a higher luxury tax threshold along with a salary floor. These in tandem would result in increased spending across the league and potentially make these contracts more team friendly in the long-run.
Having said all that, even if you sign both of them, the odds are at least one of them opts-out the first chance they get. I think adding both of them is possible while most our core is still young & cheap.