This is not new and is around for at least a few years, but might not be something you have formulated in your question. Not to be confused:
1. What you are asking for is a connection between a classic ECC and S4H. This is integration between two ERP systems, one of them being a full-function and the other one that SAP promises will cover a lot of processes (we will need to see that in action, for now it's not much, consult the post S/4 HANA is not actually a new 'Business Suite'... | SCN)
2. What you are not asking for, but might have that in mind is SLT/SRS/DS between existing mature ERP system and a standalone HANA instance for the sake of real-time reporting, etc. This is called a side-by-side scenario and is partially covered by HA300 course and this post HANA Live implementation (sidecar scenario) | SCN
Hope this helps