ABC News confirmed earlier today that Charles Gibson has set Dec. 18 as his final broadcast on World News -- one week later than originally predicted -- paving the way for successor Diane Sawyer.

The only thing we don't know now: Who is replacing Sawyer on Good Morning America?

The rumor mill says George Stephanopoulos, arguably the next best-known news anchor at ABC after Sawyer and current host of the network's Sunday morning political show, This Week.

This is a move which may make sense in ABC's universe -- after all, their last two top anchors have come from GMA, so placing Stephanopoulos there puts him in line of succession to Sawyer -- but it doesn't make much sense to me.

Stephanopoulos is certainly an able anchor, but it has taken him years to distance himself from his past as a Clinton political operative and develop hard news gravitas. Why water that down by sticking him in the soft news parade on GMA? (Sawyer and Gibson, arguably, had more and better hard news credentials before moving to GMA)

ABC's biggest problem, halted briefly by Gibson's tenure, is that they have not done well in developing potential successors to their top anchors. think of NBC, and even though their current hosts are quite successful, there are any number of staffers you could imagine stepping up to take the top spots on Today, NBC Nightly News or even Meet the Press, if needed.

But ABC has never had a deep bench, as proven by the problematic decision to replace Peter Jennings with anchors Bob Woodruff and Elizabeth Vargas after his death. Gibson's short time in the anchor chair hasn't given ABC much time to develop new blood.

So do you pull Terry Moran from Nightline, which also doing quite well thanks to NBC's Tonight Show missteps? Do you promote news anchor Chris Cuomo, who doesn't seem to have the chops quite yet? Move Bill Weir from weekends?

Hire George Lopez from TBS?

Not a lot of great options. What do you think?

Click below for ABC's official announcement:

From Jon Banner, executive producer of World News with Charles Gibson:

"It’s that time of year in this great country of ours when we give thanks for family and friends and focus on the things that matter most to us.  It’s no different here in the newsroom, where we are preparing to see our very good friend and anchor off as he begins a new journey. 

"We’ve known this day was coming; Charlie first told us of his desire to retire in early September.  As he said then, it’s the right time for him and his amazing family. 

"So today I wanted to let you know that Charlie’s last day as anchor of World News will be December 18.  We’re going to spend a good deal of time during his final week on the air looking back at the stories Charlie covered, hearing again from some of the remarkable people he interviewed, and paying tribute to our friend and colleague, and the enormous contribution he has made to ABC News over the last three decades."