Will the RS see a surge in sales and if so will there be enough supply?

[Lee]

Yes.
No.
My take is that the driveshaft issue is not as significant for the RS, as there is less travel in the swingarm.

Not sure I follow. The valve is there for drainage so I can't see how a difference in swingarm arc travel would affect entrapped moisture / water.   Besides, Darrell's RT has the valve from the factory. Surely that has similar swingarm travel as the RS ...

There's very little forward and back movement of the driveshaft on the RS, R and RT so even with rust there's not much chance for damage to the splines.
To be on the safe side BMW is putting the vent in all the Wethead bikes at the factory.
The older pre wethead bikes had more movement of of the spline area.
The K75 was probably the worst of the bikes for spline damage. It was not unusual for a K75 to have worn out splines by 60,000 miles.
The hardest service was lubing the clutch splines on the Brick K bikes. The transmission had to be pulled back.
I think we had the dealer do this every 20,000 miles or so.