I am not sure, but I believe I read somewhere in the published AAO and BALCA decisions that it MIGHT cause a problem there is a substantial difference between the salary stated on the LC and the salary paid during I485 approval, particularly if the beneficiary worked with the company all the way through (as H1b for example).
The argument made by the service goes something like this:
The day you filed the LC for this beneficiary, you stated X$s on the application. You also advertised the position with X$s per week salary. In fact you already paid the beneficiary 1.5X$s. By understating the salary for a position with these job duties in your company, you in fact deterred qualified american workers from applying for the job.
As long as the salary on the advertisement and labor cert is somewhere in the range of your actual salary, you should be fine. If on the other hand, you put the future, expected salary on there, you are in trouble if your actual salary in the same position doesn't reach the stated salary.
The argument in that case will be something like:
Yes we know it is for future employment, but by paying the beneficiary in a substantially similar position 0.6X$s we doubt that the position you advertised for the LC actually existed in your company at that time.
So, from how I understand it, the attorney should put something in the range of your current salary there (and of course it has to match the 'prevailing wage' for a position of this level).
If it increases later (and your job description stays the same), they will congratulate you for beeing a good worker but not cause any troubles. (If on the other hand you become a manager in the meantime and your job description changes, it becomes a different ballgame.)
(not a lawyer, these are dark recollections from reading up on this stuff a couple of years ago)