I slightly disagree about Morrow and being a Top 4 RHD (maybe top pairing). A year or most of year in the AHL will go a long way to prepare him for a Top 4 role. Offensively and skating-wise, he's nearly capable of that now. His deficit is on the pure defensive side of things. In his 2 game audition, he clearly made mistakes, but most that I recall had more to do about gaps and not anticipating the speed. As each of the games progressed he made adjustments, but he's still not there yet.
However, having a Slavin or somebody similar baby sit him on the defensive side of things (which he's done for Dougie, Tony, and, frankly, Burns too) should not be overlooked. Playing with Slavin, in and of itself, will be an education for Morrow, should that situation materialize.
I'm not suggesting that he will be able to or should step into that/those roles. I'm merely saying I don't think it is beyond reality that the organization expects him to be ready or nearly ready for a Top 4 role.
A lot of the blue line's future, IMO, depends on Nikishin's transition to the NHL. There's no guarantee that he will be able to "just step into a Top 4 role". I'll be quite interested in his potential late season audition or the following year's training camp.