According to Dave Meltzer in the latest Wrestling Observer Newsletter, Abyss and Sonjay Dutt are indeed WWE bound but will actually join NXT in a backstage role. Neither man will be wrestling either there or on the main roster. Abyss hasn't done much for IMPACT Wrestling for a while but was working there behind the scenes for quite some time and hasn't been under contract for some time now.
As for Dutt, he's been working alongside Jimmy Jacobs in IMPACT as a writer for quite some time now and was actually under contract through this September. Surprisingly, IMPACT was willing to release him from that because they didn't want to stand in the way of what was a better offer from WWE. That points to the relationship between the two companies being considerably better than it once was.
WWE is looking to expand NXT and they brought in Dutt and Abyss because they've worked closely with Jeremy Borash and know they'll make a great team. As always, we'll keep you guys updated.