I voted for new Batmobile, just because that seems the most useful and practical for getting around the city (can't land your jet on a roof, a motorcycle doesn't offer much protection/security, a boat severely limits where you can go, etc.).
Just another car...maybe a modified tumbler.
Something I didn't like about the other four films is that they kinda seemed like an excuse to sell toys, dragging everything out, each film (a different car for each, augmented with some other vehicle like a plane or boat, which got all bashed up and wrecked).
Keeping with the more grounded tone of these new films, I don't want to see something a complete 180 from the Tumbler, but rather something close to it, but improved. As though, once the Tumbler was destroyed (if that's going to happen), Bruce and Alfred (and Lucius) take the opportunity to roll out a second one, but fix a few things (perhaps sleek it up, add some new capabilities in the form of weapons or electronics, etc.).
But I don't think a sleek, elongated car with bat scallops and bat logos on it fits or makes sense. I much more like the idea of a bulky, rumbling ATV tank that you
cannot get to, and that is quite intimidating in its own right, just sitting there.
I don't want to see anything remotely approaching the cars from the first four films, sorry.
If they've got any balls, they'll give him a BatSegway.