no. if there are vacancies in the higher class, the passenger, can, on payment of difference in charges, can travel in the higher class. But at present, there is no system for eticket holders to pay this difference in cash and travel.
upgradation occurs only when the berth is not reserved for the whole journey, like for eg. ndls bct contains 70 berths out of which 20 are vacant totally (quota seats excluded), the next lower class passengers get upgraded w/o any charges. the cycle goes on till the wl numbers gets reduced.