I agree that new technology brings new functionalities, but the existing legacy system  is already working and migrating all of them into new tech is going to be costly, risky, and time consuming. no one will ever shutdown the running system and install a new one. the best approach that I have ever seen is step by step migration. it is more realistic and the least level of risk is involved. The approach that I am familar with is to prototype pieces of the old system with new tech and run it through different analysis. that will help  to better understanding as how to utilize the new tech and how to migrate.

usually these kind of migration  starts with interfacing with the legacy systems and replacing the current business object one by one and very carefully with the new tech implementation.

there are loads of learning curve involved in every different industry that will show up in such process. but jump right from the old system into a new one just for the sake of it is not really adviced.