I can't imagine a situation where NRL clubs will ever go backwards when it comes to the number of sponsor logos allowed, sizing, colours, etc. It just won't happen. Even if all clubs were in a position financially where they can get by just fine with less uniform sponsors, they're not going to turn down more money - and if the NRL tried to impose restrictions, I'm sure the clubs would kick up a fuss. The only spot I can ever see going away is below the collar, simply because that position has seemed to be a revolving door for most clubs over the years. It seems like companies don't really value that position very highly.
When it comes to jerseys sold at retail, I could definitely see a market for a sponsorless category - but it really couldn't be identical to the on-field version. The two Origin teams have cotton versions of the on-field jerseys with proper, traditional collars and in the case of the NSW one, it's without the big Brydens Lawyers logo. The designs aren't exact copies of the on-field jersey but it's more of a fashion, lifestyle shirt. You could sell something like that for each club in addition to a fully sponsored on-field replica.