One thing seems likely to me, and that is that SQM will likely produce as much as they can at high prices. They have an 18 month or so turnaround (depending on weather and dust storms etc) from pumping into the ponds to production - so it will not be easy for them to turn production on a dime - unlike hard rock processors. So we are entering a period of uncertainty. They will also probably assume a negative weather event at some stage in that period, where output will be severely curtailed. Finally they will probably suspect that they can start new negotiations in about 2025 (or so), years before the end of the agreed period and who knows what the regulator will agree to at that time.
So I suspect they will go for it like crazy, and pump out more rather than less. That is what I would do if I was in charge. The deal offers a lot of flexibility.
There will be a lot of busy concreters up there very soon laying out evap ponds. As the evap happens in stages, they actually do not need to have the whole thing laid out to start the clock. They can build the initial ponds and fill them up, and then build the next stage ponds ready for transferring etc when stage 1 evap is done.
On another angle - I suspect there will be water table requirements, as the limited plant life up there will possibly have deep roots to tap into the water - but if the water table was to fall too far - maybe that would damage the ecosystem. However I'm not sure to what extent the acquifers at different levels are connected to each other, and the scale of pumping versus the size of the aquifers.