"Next phase" refers to the upcoming stage or step in a process or plan. It signifies progression or advancement to a new level or level of achievement. Full definition
They are now well equipped to continue their success into their exciting next phase of education. (qaeducation.co.uk)
Then next phase is when the dog demonstrates comprehension of the skill, when we then implement the word «good» and begin intermittent rewards. (sitmeanssit.com)