I'm a Hohokam archaeologist in Phoenix and I think I can answer your question. 1st. Hohokam is a what archaeologists call the suite of cultural traits present withing a society which flourished in the southwest from about A.D.450-1450. It's not a tribe or an ethnicity. The name is derived from "Huhugam the O'odham (Piman) word for ancestor. Hohokam culture exhibited fluctuations in areas of emphasis over time which culminated in the pre-Classic to Classic transition around A.D. 1170. This included a de-emphasis of the Middle Gila River area in favor of the Salt River as the center of population as well as culture.

Most apparent within the culture was the emphasis on canal based agriculture as well as the use of Red-on-buff pottery and the presence of a marine shell trade complex. After the classic transition red ware pottery became popular and after AD 1300 buffware pottery wasn't made and a new pottery called Salado Polychrome became very popular pretty much everywhere.

If you're really interested check out The Hohokam Desert Farmers and Craftsmen by Emil Haury. He is the godfather of Hohokam Archaeology.

So anyway, the defendants of the Hohokam are the O'odham people. The Tohono O'odham (people of the desert) and the Akimel O'odham (people of the river). However, in prehistory the suite of cultural traits that archaeologists use to identify archaeological deposits as "Hohokam" we probably shared by many different ethnic groups. Especially around A.D. 800-1300.

So yeah there is the linguistic connection. When the O'odham went on their march of conquest they called to the Rain Magicians in the platform mounds in O'odham and the magicians called back in O'odham. . That's the linguistic evidence. As for genetic evidence there isn't any because the genetic testing of human remains is forbidden.

All that being said, it makes no difference really. The O'odham are the descendants of the Hohokam. Within the discipline, there isn't really any dispute regarding that. The link between the two is accepted.