In Psalm 23 we get "the Lord is my Shepherd" implying that no matter what our station is in life, or what our gift is in the church, or whoever we are that He is the Shepherd of us all. We have a direct link to Him the One Who knows us perfectly, better than even our closest friend on earth could ever know us. And we can go directly to Him. Every one of us.
But Scripture teaches that the Lord has given gifts to the church and that one of these is the gift of shepherds (pastors, Ephesians 4:11) As the following verse tells us they are for "the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ". Their responsibilities include feeding the flock of God, taking the oversight and being examples. (1 Peter 5:2-3) They are used of the Lord to help maintain the flock. We need these pastors/shepherds to help us along in the path of faith.
In order for one to fulfill this ministry it implies that he is mature himself. Not that pastors can never fail. They have and will. Failure does not negate the gift. They too need the Shepherd.
The fact that there are pastors/shepherds in the church does not imply that there is no need for the Lord as our Shepherd. Far be the thought. He still is the Shepherd of us all. And as the Chief Shepherd He is the One that the pastors/shepherds answer to and from Whom they receive their rewards. (They must give account to God for our souls - thus we submit to them).
"When the Chief Shepherd shall appear, ye shall receive a crown of glory that fadeth not away." 1 Peter 5:4
So to answer the question, Who will shepherd the shepherds? is really quite simple. "The Lord is my Shepherd."