They did make the decision before to make the .480 SRH a five shooter... then they only made about 50 of them (all Alaskans) and quit. When I heard they were going to make .480's again, I assumed they would be five shot. I was wrong!
Just guessing.... 50 is probably their minimum production run and they probably looked at their added costs (5 hole versus 6 hole) and decided it was not worth their while (not to mention sales from the 454 version reducing the buyer pool). They may also have determined that the "issues" were still present in the 5-hole versus 6-hole. Never had any significant issues with my 6-shooter.
I was pleased to see that they are reportedly going to produce the Alaskan in 480 Ruger again. I intend to get one when I start seeing them hit the stores. May even break down and do the online thing which I resist doing.