I can't imagine there's any way you could draft in a replacement synchro leader; surely it's the most demanding position on the team after number 1? Given that some people have mentioned that Lingy's been advised to rest his shoulder for 6 weeks, I'd guess it'd take longer than that to train a replacement.
Total wild guessing here, but I'd say if anything was going to happen it'd be a delay to the start of the season while he recovers?