Unfortunately, no details have been confirmed. All we know is the saber will be appearing in The Last Jedi, but it's too soon to tell any details of the prop.
"Star Wars: The Last Jedi, the Definitive Preview"
Vanity Fair released an article containing a few TLJ photos, including this shot of Rey with her saber. It appears photoshopped and still doesn't confirm anything for sure, but it does disprove the "no rivets" theory caused by the product packaging.
Star Wars Celebration Orlando
Unfortunately, the teaser released at SWCO did not give a good look at the saber hilt. The only glimpse we got during the event is this far off behind the scenes photo of a stunt saber.
Source: Star Wars YouTube channel
Note: It is unclear at this time if the product packaging includes the actual screen used prop - and it is possible it has been heavily photoshopped. Only time will tell for sure. This is only observation based on this one picture.
TLJ packaging design revealed, possibly giving first look at new saber prop