The 772's are up for replacement, that much is certain and has been publicly announced in the above linked article.
The 787-10 seems the most likely to me in terms of lead time and commonality. The 777x is an option on the table, but I suspect it's too far away. Lastly, the A350 has also been mentioned, but I suspect the cost of adding another fleet will be prohibitive compared to a 787-9/10 mixed fleet.
Last edited by ElZilcho; 15th Jun 2017 at 10:33.
Reason: Misread the OP!