It's not clear that Ripple Labs is any worse off honoring the option now than they were; in either case it's a fixed fraction of their holdings.
Edit: Let me explain this again. Let's say the option was exercised last year; Ripple Labs would be out XRP that is now worth ~$1B. Now let's imagine that the option is exercised right now; Ripple Labs would be out ~$1B of XRP. It's the same thing.
You're focusing on the wrong thing so let me explain again as well...
It's not about the beancounters realising the option is way bad for the issuer, it's management getting cold feet about signing off on 5% and mispricing future trades.
Edit: Let me explain this again. Let's say the option was exercised last year; Ripple Labs would be out XRP that is now worth ~$1B. Now let's imagine that the option is exercised right now; Ripple Labs would be out ~$1B of XRP. It's the same thing.