Many factors to consider before you go for it:
1. What is the basis of arriving at this conclusion?
2. Scope of SAP ABAP around your geographic location
3. How strong you emerge in SAP ABAP after your training
4. You will be starting your career from a scratch – are you read for that?
5. Why you lost interest in System and Networking after 3 years once you chose it as your career 3 years back?
You have to introspect yourself for these answers, otherwise career wise it has a good scope.