THE FACTS:
With the change to f2p, the workshop will be moving from its current subscription based ("open") system to a manually approved voting queue ("closed") system.
The intended goal of this transition is to monetize workshop content.
The primary changes will be:

• Changing from a subscription-based system (eg Left 4 Dead 2) to a vote / queue based system (eg Chivalry)
  
• Submissions will be manually approved instead of open [1][4]
  
• Workshop authors will have the ability to charge for items, similar to the Dota 2 workshop. Note that items will not be tradable.
  
• Existing workshop constraints will be lifted [2]
  
• FOR EXISTING (pre-f2p) HIGH-QUALITY CONTENT : Puny Human Games will attempt to "work with the authors to provide it for sale" [2]
  
• FOR future (post-f2p) HIGH-QUALITY CONTENT : Workshop authors will have the opportunity to offer their items for sale, with Valve/Steam and Puny Human Games taking a cut
  
• For existing low-quality content : Low quality content will be culled appropriately ("i imagine 80% of it will remain, with the other 20% being old/useless/never downloaded/something that is no longer necessary" [2])
  
• For future low-quality content : Low quality items may or may not be approved[3]

Discuss.



[1] Joshua Ashton, Steam PM, first week of Augest (approx)
[2] Urinal-Cake, Discord PM, 2017-07-17
[3] 2018-02-01 : This is no longer true.
[4] 2018-02-01 : This may or may not be true.

ed 2018-02-01 : items will remain free by default.
ed 2018-02-01 : removed earlier edit.