Yes it will going decrease but in certain situation.
If technology become common and lots of developers are in that same technology then changes are high that rate will go decrease.
But at same time you will find something latest, something complex and something which needs mastery to accomplish - for this salaries will remain high as it is.
'I wonder what would happen, if there were a language so complicated, so difficult to learn, that nobody would ever be able to swamp the market with programmers?' - Bjarne Stroustrup [1]