3GPP has been engaged in further advancing the evolved E-UTRAN and UTRAN based radio access network technologies. NR is the 3rd Generation Partnership Project (3GPP) endeavor for outlining and standardization of 5G advanced radio access technology. 3GPP has released the first set of 5G NR standards, that is, the non-standalone 5G radio specifications. As LTE technology is massively deployed and broadly accepted, the transition from LTE to 5G is very critical, and it is of maximum importance that the backward compatibility of 5G with LTE is considered. 3GPP has identified several architecture options for 5G. This article gives an overview of the NR architecture options, their deployment scenarios, and the key migration paths. LTE-NR dual connectivity (DC) is presented. This DC scenario is unique in the sense that DC is being endowed for two different generations of 3GPP radio access technologies. We further present the integration of MPTCP with LTE-NR DC and DC-like aggregation, that is, 3GPP-non-3GPP interworking to bring in the advantages of MPTCP in terms of link robustness, reliability and dynamic mapping between the traffic flows and the available paths. Finally, we discuss future research and standardization directions of the next-generation networks.