More realistically in the short term...
A large "lighter than air" unmanned probe that would be able to map the surface of Venus with radar, or preferably, something with a shorter wavelength (not sure if that would work). A large vehicle could drop something like the old "cloud cars" that zeppelins used to drop below the clouds to see things. I think the lowest cloud layer is at about 35 km, but I could be wrong. A balloon that worked by heating the atmosphere inside would last longer than one that used a different gas.
Getting it down from space into the atmosphere would not be a trivial problem.