Ruger seems to try new calibers fairly often -- and then if it sells, add more models. If it bombs, cancel it.
They tried 327 Federal when the cartridge first was introduced, but lack of ammo make adoption slow, and the 327 Ruger's were discontinued.
But then Ruger tried again and introduced the single 7 version of the 327 Federal -- and it was successful.
So they added the LCR and the SP-101 version.
Now they are trying the 10mm/40S&W in Redhawks and Blackhawks. If those sell well, then perhaps a GP-100 five shot will be coming at some point.