It was reprinted in 2005 as Elmo's Delicious Christmas, according to this Amazon listing.
It's been reprinted again in 2007, also as Elmo's Delicious Christmas, but with a different ISBN, and altered credits -- it now says "Written by Michaela Muntean and Elizabeth Clasing".
I don't have the 1999 or 2005 editions, so I can't check on this, but I think a couple things have been altered. Elmo has an Aunt Sue in this book, who looks like the 1990s version of Elmo's Mom. Both Mom and Aunt Sue are mentioned in the text, but Sue is the only one pictured. Also, Luis appears in the illustrations, but isn't mentioned in the text.
My theory is that Dalmatian reprinted the book in 2005, with an Elmo-friendly name but otherwise unaltered. In 2006, Talk, Listen, Connect officially established a different look for Elmo's mom, so Dalmatian had to change the book in 2007 to remove the red mom. They altered the three illustrations of Elmo's mom, adding "Sue" onto her apron to establish that this isn't his mom. Elizabeth Clasing edited the text, changing mom to Aunt Sue, so she's now credited as a co-writer.
I think Luis' name also may have been taken out of the text, either for the 2005 or 2007 edition. Every other character in the illustrations is mentioned, except Luis.
The cover that's pictured is the 2007 edition; I'm not sure if there was a different cover in 2005.