We home based at HMSP and/or buddies close by homes, for the entirety of Feb, March and April, typically fishing weekdays and abstaining from weekends, from the late 80's up to the closure in 2009.
The Sauk would see anywhere from only one or two boats and a handful of bank anglers, to possibly 20 boats and about half that many bank anglers (spread amongst the various drifts), numbers increasing towards the end of the week through the weekends.
The Skagit above Rockport would see little to no pressure during the same time frame, with the section from Rockport to Faber's seeing heavy pressure. The stretch from HMSP launch to the Sauk mouth, down to Mixer Bar, Leaning Cedars, Island Pool etc, was particularly hard hit by sleds and guide boats, with a bit less pressure from Faber's to Concrete (predominately sled traffic). Hardly ever fishing below the Baker I can't comment on angler numbers below that point.
In review I would estimate the combined number of anglers on the Sauk from Mill to the Skagit confluence, and the Skagit from Marblemount to Concrete, to be somewhere in the range of 25 to 150 (depending on time of week and weather/river conditions). Those numbers seemed to hold pretty consistent from season to season until about 2005, then increasing until 2009.
I understand the main goal of OS is just to get a Skagit/Sauk C&R season up and running again. However, if guide reform/restrictions are not adopted, a special C&R permit is not implemented (to help offset drainage specific enforcement costs), and angling methods see no modification, this dream will be very short lived. It will see a lifespan of two to three seasons, max.
The above angler numbers will absolutely be double what they were prior to 2009... 25 going to 50 wouldn't be a huge deal, 150 jumping to 300 would be devastating.