First batch will likely replace old or not refurbished fleets. There are two un-refurbished 772s that OZ tried to return to lessor last year - I think initial two A350 frames will replace them and fly to CDG. And then Asiana is slowly retiring 747s. Just retired one of two 744-combi about a month ago. No news regarding aging 767s as of yet but A350s (any variation) will eventually replace these fleets.
Usually in the mid-Feb, Asiana announces fleet change that includes both new deliveries and fleet-retirements.
Don't expect route announcements from Asiana for now. With a rapid rising of LCC, both Asiana and KE are struggling. Some analysts even predict that Asiana may not get A350s due to financial problems (which is an overreaction, I think).