Here is a succint and informative MU-616 reality check reply found online in reactions to New Avengers #2. If taken at face value our new "Universe 8" not only reveals a huge spoiler of how Secret Wars #8 conclusion will end, but will beg a bunch of questions. There doesn't seem anything inaccurate about calling it 616 or U8 interchangably at this point. More answers are obviously forthcoming - for good or bad - but in the meantime maybe some MUMBers want to see this...
It's the 8 universe, while old 616 was the 7th.
Still earth 616. With tweaks and nips and tucks.