"It is likely they'll (the industry) come to the government in the next six to 12 months with their own suggestions of what they might do," he said at the Trenz tourism event in Rotorua.
The Government had in a "rare move" allowed Stewart Island to impose a $5 visitor tax and differential charging regimes were in place in overseas.
"It's not a new concept but whether we want to actually do it and how it would apply - all of those things are a long way down the track."
The $12 million fund - to be spent over four years - would be administered by government and private sector representatives.
In the South Island in particular freedom campers without access to public toilets are causing problems in small towns.
Key announced an $8 million boost to target key growth markets such as India and the eastern seaboard of the United States.
He also announced:
• $2.5 million for Te Puia, for new facilities at the New Zealand Maori Arts and Crafts Institute in Rotorua, including a new bone, stone and pounamu carving school, a ta moko (Maori tattoo) studio and a taonga gallery.
• Just over $1.2 million for Timber Trail Adventures Limited for the development of an 80-bed lodge located at the halfway point on the Timber Trail cycleway at Piropiro in the Waikato.
• $500,000 for Queenstown Bungy for an innovative world-first bungy launch system at their Nevis site.
In Wanaka on Sunday he also release details of further funding for cycle trails.
The government had spent $60 million the New Zealand Cycle Trail, which he said had already been extremely successful in helping attract high-value visitors, getting them to stay longer and encourage flows of visitors into the regions.
In January 2015, 125,000 people used the New Zealand Cycle Trail, compared to 97,000 in January 2014.