The bigger issue long-term is going to be replacing Brian and his abilities. Fairfax will always have a large bond portfolio because of its insurance business. Finding someone as gifted as Brian may be a 1 in 1,000,000 problem.
There is the new young guy that people say is doing great, but Brian made certain calls over his career that were just extraordinary. He is arguably one of the greatest fixed income managers in market history, especially over the duration of his career and the market beating results he has given Fairfax. He didn't just beat his peers, he killed them...over decades!
This is where the young guys like Wade and Lawrence will influence the equity side to provide more steady, consistent results rather than as lumpy as we've been used to. But their smoother earnings on the equity side may be tempered by lesser results on the overall bond portfolio.
Nonetheless, Fairfax only needs a 4% return on the entire portfolio to hit its 15% ROE target. Combine that with a well-run insurance business, they should be able to hit their past return of 17% annualized. Cheers!