Possibly the best solution there is, Although Bobo is in his penultimate season in his current training bracket and already at 7* He possibly is still worth one last push, although your right that a 18 year old fast training Kofi Bobo Jr bought at the start of next season will seem more beneficial.
For anyone wondering the training brackets are 18-21, 22-25 and 26-29. 25 is the last ideal age for power training but it still can be done for 26-29 year olds in exceptional circumstances like dv8r did with Petersen to keep him in the team for longer.