How to manage legacy , high volume OSS/BSS stack 5 years down the line?

5 year down the line - the legacy can be transform to the Cloud with the help of SDN and NFV

In my opinion, the rationalization of the business processes and the data is the Key. The issue is not the OSS or the BSS capabilities but the lack of standarization on the data models and the multiple business silos working in different ways. A way to improve could come from a definition of an consolidated OSS-BSS roadmap which looks how to progressively remove unnecessary capability via more efficient use of the existing OSS-BSS, developping capability gaps and a common use of data but withouth introducing very disruptive transformation plans that at the end tend to fail. The OSS and BSS should be managed as a single entity addressing more holistic business needs.

Medium-term 5 years ahead? It should be rather pragmatic - count all the platforms and check the use of those. Sometimes you will be surprised that the platform is not used at all - then can be phased out .  And the cost of “umbrella platforms” exceeds the cost of new standalone platforms 2 to 1 minimum.

I think that the solution is a good Big Data implementation, a good Big Data Lake with a clear Governance. Firstly you need to analyze the quality of data, clean it and differentiate between static data (customers, services, etc) and dynamic (service orders, invoices, appeals, information contacts, etc) to define archiving policies and On-Line needs

My take on the question: take a long hard look at your current BSS/OSS stack and check if
- you’re happy with the performance and scalability (and therefore cost) of IT vs customers managed
- are you REALLY in control of the asset base through fully auditable commercial and service orders [many telcos are not, even in 2020]—> if that is not the case, start working today. You said your stack is large volume, so getting this right while keeping the risk in check will take time
- when your asset base is under control, start thinking about NFV/SDN impact on your catalogue/services/asset base—in 5 years time, the technology will be real and maybe you’ll be in trouble when tyring to procure “good old” network elements because there’ll be nobody left to sell and service them for you

Jose and Leo - nailed it - on key critical directional elements for today and the next 5 years - one has to be very cautious and thoughtful - when plotting a 5 years course - and avoid to create a new set of silos with its own umbrella systems -

The OSS/BSS roadmap is depending on the products that must be provisioned/billed. So the key is the product management, who is demanding the requirements to BSS/OSS. With new technologies like 5G/iOT/AI there will be new products demanding new requirements to BSS/OSS. According to TMF the provisioning/mediation chain (and following topics) are serving the demands of the products sold by marketing.
5 years is a long timeframe considering the current technology improvements. So I would rather look into 1-2 years in time for any business calculation.