See title. This is really great news and will certainly make it a lot easier to plan out your team and send over any items you'd like. Source: IGN's Review http://uk.ign.com/articles/2017/11/14/pokemon-ultra-sun-and-ultra-moon-review
OH, YES! I was worried about this, but now I can confidently make my way through alola again with my trusted team.
I already knew it would be based off of past games. You're probably restricted to trading over things that were available in sun and moon, meaning none of the new stuff can come over. In gen 6, you couldn't put new megas into X and Y from ORAS with the eception of the mega latis. In black and white, the new kyurem forms couldn't come over nohr could the new keldeo form. Or in gen 4, you couldn't put a spiky ear pichu into DPPt even if you tried to hack it in (kinda a stretch on that one but you get the point).