Players have been clamoring for an increased stash size in Diablo II for years, but making it happen in the upcoming v1.13 patch is apparently causing Blizzard a lot of headaches.
The decision on whether or not to include the enlarged stash size has been slightly delayed. As mentioned previously it would require some additional weeks of development and would remove one of the most requested features were we unable to include it. If it were to be included the concern is that it could render Diablo II unplayable, and repairing the issue after the fact would draw heavily on development resources. Which is also something we obviously want to avoid. Personally, I'd rather have support for higher resolutions.
We hope to be able to reach a conclusion and decision soon on the future of the 1.13 patch, and we'll keep you updated as it develops.