Of the current group:
5 are in there 60s (Gary Stevenson is the youngest at 62).
3 are in there 70s
2 in there 80s
And President Nelson is 93.
So you will very likely have 2 more in there 60s or potentially mid to late 50s. Should be interesting.
If you look at the likely pool that they'll fill those spots from (Presiding Bishopric and Presidency of the Seventy) all of those guys are in their 50s and 60s. Bishop Causse is 54. He'd be a fantastic addition, I think.