Where is Renewed Hope in the Priest talent tree?

Discipline tree, row 5, column 3. You need 20 points spent in Discipline before you can learn it, and Soul Warding must be at full rank first.

Is Renewed Hope new in WoW Forever?

Yes. Renewed Hope has no Classic 1.12 counterpart.

Rank	Effect	Source
1	Your heals from Flash Heal, Lesser Heal, Heal, Greater Heal, and Penance gain 2% increased critical strike chance when cast on targets with Weakened Soul, and reduce the remaining duration of Weakened Soul on their target by 1 sec.	client
2	Your heals from Flash Heal, Lesser Heal, Heal, Greater Heal, and Penance gain 4% increased critical strike chance when cast on targets with Weakened Soul, and reduce the remaining duration of Weakened Soul on their target by 2 sec.	client
3	Your heals from Flash Heal, Lesser Heal, Heal, Greater Heal, and Penance gain 6% increased critical strike chance when cast on targets with Weakened Soul, and reduce the remaining duration of Weakened Soul on their target by 3 sec.	client
4	Your heals from Flash Heal, Lesser Heal, Heal, Greater Heal, and Penance gain 8% increased critical strike chance when cast on targets with Weakened Soul, and reduce the remaining duration of Weakened Soul on their target by 4 sec.	client
5	Your heals from Flash Heal, Lesser Heal, Heal, Greater Heal, and Penance gain 10% increased critical strike chance when cast on targets with Weakened Soul, and reduce the remaining duration of Weakened Soul on their target by 5 sec.	client

Tree: Discipline, row 5, column 3. Needs 20 points in Discipline first. The earliest you can finish all 5 ranks is level 34 if you put every point into this tree.
Prerequisite: Soul Warding at 1/1.
Competes with: Penance in the same row.

Renewed Hope is new in WoW Forever. Nothing in Classic 1.12 does this for Priests.