The rumors, according to The Wrestling Observer, is that Hideo Itami and Finn Balor will be the next two to be called up to the main roster, despite just getting to NXT.
Yes, before Sami Zayn, Adrian Neville, Tyler Breeze, and The Ascension.
The perception around Itami, formerly KENTA, is that he's the biggest wrestling star in the world outside of the United States. Finn Balor, formerly Prince Devitt, is held in similarly high regard.
Expect them to continue as a tag team to get their feet wet.