I bought a pair of the 454C's when they came out, and I made the phone call to Ruger to ask about the 480R and 44mag versions - they said, at the time, which would have been, what, 3-4yrs ago? - they do intend to bring the 44mag version to market, pending the success of the 454C version.
However, with the advent of the Kodiak Backpacker and the 44spcl GP100, they might have refocused their efforts since that time.
Easy enough to pay a smith to cut and crown a 7.5" and slabside a standard SBH. The milled base foot for the new front sights are a little wonky, but a guy with a mill will get it done easily enough.