I'm one of those in the minority who would buy an all stainless R9 in a minute if it were available.
I might also keep the aluminum version, but an all stainless would be very nice to have in my opinion. It would be stronger/more durable which might mean that +P ammo could be used if so desired. It would have a bit less recoil. It would not wear as quickly, especially at the frame rails. Ultimately, you could shoot it more and it would last longer. It could be used as your practice gun and the aluminum version could be used as your carry gun. Both could then be handed down to your son someday.
Maybe the extra strength/durability wouldn't be an issue in reality since you likely wouldn't shoot it THAT much anyway, but the peace of mind would be nice. As to the extra weight, I don't think it would make a huge difference for carry, especially if carried in a waistband holster, which is a better way to carry a pistol in my opinion.
Anyway, it's not likely to be made. Probably about 2 years ago, long before they started actual production of the R9, I had asked Eric if they would make an all stainless version, or perhaps a titanium frame version. He said he doubted a titanium frame, but they were definitely going to make an all stainlees steel version eventually, after the aluminum frame version was in production for awhile. He took my name and number and promised to let me know when they would be available.
Then, about a year ago, Eric told me that the all stainless version was not going to happen. Probably not enough demand for it. If enough people ask though, who knows...