As far as I know there is no ETA for an ATV3 jailbreak. In fact I have yet to see any indication that anyone has found a weakness that can be exploited to inject code as is required for jailbreaking. That makes me think a jailbreak is still some way off and there is a distinct danger it might never materialise.
If the jailbreak DOES appear for the ATV3 then FireCore have already indicated that your ATV Flash (black) license will also be valid on that device.
you might be getting confused, while the atv2 does not display 1080p it can still play 1080p content in 720p. the issue is jvc’s stupid use of the .mts format. i sold my camera just because of that reason. sometime i could change the file extenshion to .mpeg and it would work. you could also use xbmc to play them on the apple tv.
if your getting streaming problems, tried wired connection and make sure you NAS net work speed are fast enough. alot of nas hds are not actually fast enough to stream 1080p content.