Dream and Mahal are both currently scheduled to be in Houston, Texas on the weekend of January 26, according to PWInsider. There's no word yet on if there are plans for them to return in the 30-Man Royal Rumble match, but they are scheduled to be in Houston and will likely be at Minute Maid Park that Sunday.
Regarding Dream, he has been at all NXT TV tapings and has been at the WWE Performance Center regularly since being pulled from the ring with a back injury in October. It was just reported this past week that Dream's back injury was said to be "pretty serious" and there was no solid word on when he will be back in action, but that return could happen soon as it was reported back in November that he was expected to be out for "a few months," which would have put him back in the ring in late 2019 or early 2020.
Mahal has been out of action since suffering a patellar tendon rupture at a WWE live event in Denver on June 15, 2019. He then underwent knee surgery in late June and it was reported that he would be out of the ring until the first few months of 2020 at the earliest. As we've noted, Mahal started teasing his comeback in December. He's noted in recent social media posts that he will "be back soon" but there's no confirmation on when he will be back.
WWE currently has 12 open spots for the 30-Man Royal Rumble Match. The following names have been announced: WWE Champion Brock Lesnar in the #1 spot, Roman Reigns, Randy Orton, Drew McIntyre, Ricochet, Rey Mysterio, AJ Styles, Erick Rowan, King Baron Corbin, Dolph Ziggler, Otis, Tucker, Elias, Aleister Black, Buddy Murphy, Rusev, Bobby Lashley, R-Truth.
Stay tuned for updates on the Rumble, and the WWE ring returns of Mahal and Dream.