I have had similar situations and I considered deferring. I talked to a couple of profs, and from my understanding, it is pretty hard to do. It would be a strong enough reason if you guys are married, if not, prob not a strong reason for them to consider. Also, it depends on if the prof really wants you. If you have high GPA, great GRE, or maybe even some conference papers, then you are in better odds for them to do it. Lastly, it also depends on their funding availability. Lets say a prof wants you to do research for them due to your previously demonstrated abilities of the area. He/she may still not be able to do it because the funding is left for only 1 more year. NSF and other funding sources for STEM majors (I am mechanical engineering myself so IDK about the art schools) often only give findings up to 4-5 years. If you are onto a bad timing then you are out too. That being said, you should talk to the prof who wants you, or the department if not a specific prof. There are just too much bureaucracy in this to know it certainly.