The basic answer to this question is no.
Disney does not discount one or two day tickets and the redsellers will generally add a premium.
There is a possibility that you could purchase a Two Day Touch of Magic ticket, which includes two days, one park per day, plus one water park or DQ for soemwhere between $99 and $125 dollars. But normally you will have to sit through a Time Share Promotion to get this type of ticket. And they are not sold on WDW and cannot be upgraded or modified in any way.