By the end of the 20th century, it seemed as if the slow descent of Venice into the sea had been stopped by a mixture of engineering and careful management. However, recently it seems that the problem is still ongoing.
However, the water is rising much more slowly than it did in the past - about 2 mm a year - and new technology is working hard to overcome the effects of this. In 2014 it is planned to install a new barrier which may slow the decline, though it probably can't stop it completely. Venice is under pressure from movements in the earth as well as the rising water, so the likeliest scenario is that it will keep on sinking until one day it can't be saved.
That day should be far in the future, provided there are no major changes in the climate or surroundings and the defences are kept up. It is even possible that a solution could be found one day. In the meantime, though, it's probably best to go and see Venice while it's still there ...