Other than Nexus 6, 6P, and 5X the only other phone I know works (kinda of) on Project FI is MXPE... WiFi and Tmo work just won't switch to Sprint. Lacks the software necessary for that function. Radio design based on the Nexus 6 so physically it could work one day if Google expands Project FI. The S7 likely has more barriers. Looking at the S6 for reference it has 14 SKUs (34 SKUs including edge, edge +, and active). Different SoC and carrier/regional specific radios driving factors. I'm not sure how many SKUs the S7 will have but I think there's no chance ALL SKUs will have all of necessary radios for best experience.... Some SKUs will likely work better than others. Some may not work at all... Hard to tell.
Posted via nexus 6p project FI