Not sure what the requirements are for the new visa for the further stay, but perviously the ILR requirements are more about are you still together rather than the salary. Also when you are ready to apply both yourself and your partner's (if working) salaries will be taken into consideration,

To be honest I would worry about the requirements you need now rather than what may happen in 33 months time. From what I understand you are not applying till next year, a lot could change by then, let alone a couple of years from now.