With the amount of Zubat you can catch, most people have an excess of Zubat candy and more often than not, we will just use it to power up our Golbat but you might want to hold on to it for a little longer because you might need it to evolve Golbat once more when the Gen 2 update arrives.
New about Niantics already working on the Pokemon Go Gen 2 have been circulating the internet and it is believed that the Gen 2 version will bring in a few more Pokemon as well as some new evolution for the current Pokemon.
It is believed that the Gen 2 version will allow users to involve their Golbat into Crobat. Some other Pokemon that might be getting a new evolution form includes Eevee, Chansey, Gloom, Horsea, Scyther, Onix and more.
So keep catching those Eevee and Zubat because you will need them soon.