There is nowadays sufficient capacity with GSM-R and GPRS for the current railway operational needs.
There is commitment from GSM-R Industry to support GSM-R at least until 2030, which will ensure the transition.
There is a risk in the technology choice (4G vs. 5G), linked to the functionality commercially available, to the expected evolution of the standards, and the availability of products. Indeed, there is no further spectrum designated for railways, other than the one currently in use by GSM-R. Furthermore, 4G standard does not include the spectrum in use by GSM-R.
A technology independent architecture model needs to be developed to ensure the split between applications (voice and data) and technology. The aim is to get to a flexible architecture, where the influence of the evolution of the radio technology is minimized.
Any new system should include GSM-R in order to protect the investments and provide continuity of railway operational communication.