This is just me theorizing with the direction of Lionel on LC/+:
If you run legacy, and it does what you want at a cost you can afford, there really isn't any reason to change any time soon. It seems LC+ is geared more to an entry level market, lower costs, competitive with just going conventional, and it brings remote command to the hands of people that may have otherwise been priced out of the market.
As for the future of the product, the radio link that exists in LC right now is capable of offering all the functionality in a legacy system many times over. I see more features being added over time until, in say 10 years or some such, a new full function system is introduced to replace Legacy, running on the 'new' system. All the LC+ out there would run on this system, but you would then need a "Legacy track controller" to connect between systems.
More simply, there is also the fact that there is an expected standard in Legacy locomotives, and if they think that a a model won't live up to that standard it is good business not to make it. You don't want someone to buy something and then say " Yea, I had a legacy engine, it doesn't do anything special" You want it to be a top end, all the bells and whistles, model.
