It'll probably be a long time before MHX comes out, more than enough time for you to get MH4U. There would probably be enough time for you to finish the game two times over with different weapons before we even get a word of Cross coming to the west. As people have already said above, all the DLC is currently out, so you won't have to wait for them to come out every month, which is what I'd assume Cross will do once it comes out.