I have a shiny heracross and I'm wondering if I can get another by breeding. Is this possible?
No the chance stays the same at 1/8192, UNLESS you Medusa method, with means if you breed two Pokemon, each from a different country your odds slightly increase. For example if you breed a ditto from japan and a hearocross from America, you have a slightly better chance of hatching on shiny, even though the odds are still slim.
Hope I helped! :D
source: experience and http://bulbapedia.bulbagarden.net/wiki/Masuda_method
No, it stays the same, there is no increased chance.