The NMRA has already adopted a set of recommended practices for standardized sockets and plugs in N, HO, and Large scales.
Many new HO locomotives are being made with this socket. Any command control manufacturer is free to make a decoder or other device that will plug into this socket whether it is a DCC decoder or not. In addition Digitrax makes board replacement decoders for many HO models to make installation even simpler.
The N-scale socket and plug arrangement that was adopted is based on a European design that works well for many European locomotives. Unfortunately, this design does not work in some US models. Many board replacement decoders have been produced for the N scale market. Digitrax has introduced a smaller version of the HO plug that will work in many US and European N scale locomotives.
The Large scale plug that was adopted does not support all the functions usually present in these locos and even though LBG has begun using this plug, it may not ever by widely adopted in its present format.