TLDR: Days of the New did it under much worse circumstances so the odds aren't out of favor for Creed.
You never know. Tool and Guns N' Roses did it. However, I acknowledge that's not a fair comparison. Guns N' Roses is a staple of rock culture on the level of Led Zeppelin. As for Tool, they have been revered for years for their musical capabilities and unique albums as opposed to the critically panned Creed. So maybe, I'll compare Creed to a more suitable band as far as reunions go. Gather round the campfire fellas, let me tell a story.
Days of the New's original lineup got back together in 2014. Keep in mind, since their inception, Days of the New has always been heralded as a Travis Meeks solo project. Much like how Gavin Rossdale and Chad Kroeger are with Bush and Nickelback respectively. He wrote all the songs, and it was his creative vision. After a successful tour, and platinum album, Travis Meeks fired the other three members of the band. He publicly called them musically talentless, wannabe rockstars, and dead weights. They would later go on to form Tantric, and even wrote a lead single about Travis Meeks and his behavior called 'Breakdown'. Years pass, Tantric's original lineup eventually breaks up due to lack of mainstream success, and Travis Meeks falls deeper and deeper into meth addiction. Eventually he robs fans through a kickstarter campaign for a fourth Days of the New album and eventually just becomes a hopeless, washed up loser. Come 2014 and against all odds, the original lineup gets back together. After Travis Meeks' horrible insults, after his unreliable behavior and well after Days of the New's mainstream success, Todd Whitener, Jesse Vest and Matt Taul decided to try the band out one more time. Part of the reason is Travis Meeks apparently begged them for a reunion in person, through the phone and through text messages. But another reason is the guys realized they were more important to the band that what Meeks originally led the world to believe. Days of the New reminded them of being teenagers again. Going out into the world, finding instant success and living their wildest dreams opening for bands like Metallica and Jerry Cantrell. Days of the New meant something to them at one point, and they remembered how much that something meant. Unfortunately, Travis Meeks did all of the actions he accused his band members of doing back in the 90s. He acted like a diva on stage, refused to sign autographs, and would bitch out soundtech saying things like "is this how you treat the singer of Days of the New?" on stage while the instrumental members hung by in embarrassment. Eventually Travis Meeks got too fucked up to play and the band abandoned him onstage, thus breaking up the band and ending the reunion once more. Meeks has been in and out of prison since then, and if you want to look up his mugshot on Google it will absolutely disgust and sadden you.
In conclusion, while Creed is not some major band like Tool and Guns N' Roses, they are bigger than Days of the New. Stapp is not a hopeless basket case anymore and he's doing very well for himself unlike Travis Meeks. Overall, Creed is more on the lines of a band like Silverchair or Mudvayne, where they may not be the number one list on bands the majority of rock fans want back together, but should they do so it very likely will be a success because of their hungry dedicated fanbase.