If I were Rockstar and I was bringing it to next gen I wouldn't announce it until at least next year. If they announce it now, some people will hold off buying it for the current gen. If they announce it next year, some people will buy it for both.
It makes no business sense for them to announce it at this point.
I guess your right, but if i buy it for the 360 on release i wouldnt buy it again for next gen UNLESS it really is mindblowingly good.