All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Hajj is obligatory upon the Muslim individual who is physically and financially capable without delay as clarified in Fatwa 87129. Thus, if you are physically and financially capable to perform Hajj, then you have to hasten to perform it without delay. This actually takes precedence over paying the expenses of the Hajj of someone else.
If you have much money in a way you can fulfill your promise and perform Hajj in the same year, then do that; otherwise, give precedence to what Islam obligated you to do, i.e. perform Hajj on your own behalf.
If you made a promise to Allaah The Almighty with a wording that indicates commitment to pay for that person the expenses of Hajj this year, then you should pay an expiation of breaking an oath if you cannot fulfill it, and pay the money for that person whenever you are able to do so. However, if you did not utter a wording that indicates commitment, then you are not obliged to do so. For more benefit, please refer to Fatwa 83652.
Allaah Knows best.