They've been cute and flirty with each other at press events and there's that one picture from Lupita's Instagram where it looks like she's wearing Oscar's shirt (it's one of the 'Estat Guars' shirts his uncle made for everyone but it looks like his name is printed on the sleeve). It could easily just be normal cast friendliness and Oscar at lead seems to flirt with everyone, but they would be such a gorgeous Hollywood power couple that I've latched onto the idea.