Seeing that the .480 chambering has been fading towards discontinuation in the SRH line, I doubt it'll be a single action offering. Of course if it's important enuff, there's 'smiths that build one for ya.
I would buy a SRH or Bisley (as long as it has adjustable sights), even though I already feel my Centerfire Single Action Collection is complete with only the Blackhawk in 45 colt...
The reason is that I just really like the 480 Ruger chambering. I will never part with my Ruger SRH in 480 Ruger
I think my custom .475 bore Blackhawks will continue to be 475 Linebaughs.. That gives me the option to use 480 brass or 475L brass... A second cylinder might be nice but that is a chunk of change extra just so I can be a little lazy about cleaning my chambers...