Thanks shaoron88 for letting me know about this ;) The scans were provided by the forum CLAMP in Forumland. According to the forum, a XXXHOLiC guide book will be released in March.
This supports what was previously informed in the tentative Bessatsu Shonen Magazine cover that was posted in the magazine's official blog. Foreign publishers of XXXHOLiC also announced recently that volume 19 would be the final volume of the series.
Even though the cover was later edited and CLAMP-NET.COM didn't mention Chapter 213 as the final chapter, it looks like it was only to keep it a secret for a bit longer.
XXXHOLiC ends with 19 volumes, becoming the 2nd largest CLAMP work, only behind Tsubasa, with 28 volumes. Although if X ever returns, it shall take XXXHOLiC's spot since 21 volumes are planned for X.
Makes me think that XXXHOLiC's move to Bessatsu Shonen Magazine happened to both boost the magazine's sales while at the same time give CLAMP a more flexible workflow with monthly deadlines instead of weekly. After all, only two volumes were published in the magazine.
Truthfully, I am very relieved with this news, XXXHOLiC's development fell greatly since its move. As stated by CLAMP (through Dark Horse), the series became longer than planned, and it was suddenly extended at the point where it should have ended.
The story as it is still has a few points left unresolved, we'll see what CLAMP will deliver for the final chapter, but we know that it's not unusual for CLAMP to make open endings, their stories and characters are all part of the same universe and they keep going through their other works.
This will give CLAMP more time to focus on GATE7 and hopefully maybe even restart one of their halted series. My first guess would be Gouhou Drug, since Nekoi will have a lot of free time after XXXHOLiC ends and we know how much she misses that series =)