I think the only real advantage of cinema is them showing things before you can stream them, if that changes and films come out at the same time as they do at the cinema, that'll be where you see a real dip in cinema numbers.
Will the film industry do that, I don't know, there is already a gap in release times globally, which IMHO contributes to piracy (people want to see stuff as soon as its available so will download it if they cant watch it locally at the cinema) global release dates would increase numbers I think, but if those gaps remain, and you can watch it at home, cinemas screwed..
I do think them showing older films/trilogies etc is a good idea though, and this is something they should look at expanding as well as showings of other things, not necessarily films, would be an interesting avenue to explore.