What would be really fun, since it's so damn far off and they're filming anyway, would be to film some sidebar-snippets and "leak" those. Nothing from the actual film. Just bridge scenes. Clark glancing at a headline scene, Daily Planet office chatter scene, a Lois off-screen scene, droning on and on about Bruce Wayne, with a dead-pan "enough already" close-up of Clark's face. Just anything to tie Clark showing up for work (last we saw him) with other superheros making their appearance in his world (without us seeing them...yet).
Create some buzz that way, small universe-building snippets, rather than temp actual leakage to fill the insatiable demand for insider info.