The Defense Information School (DINFOS) will begin training (and releasing military news) in Spanish (along with English) because it will be in its self-interest so much that it will be self-defeating not to do it.
The turning point will come when warfare starts and continues for a prolonged time in a Spanish-speaking place.
DINFOS will drag its way toward becoming bi-lingual for the same reasons that civilian society does. Americans hold an English-only identity of the country. Population changes are forcing the acceptance of the Spanish language gradually in more and more aspects of civilian life. Still, imagining armed forces leadership for the defense of America, in a non-English language will feel wrong longer than it does for many more-mundane aspects of life.
Still, the reluctance will only postpone the inevitable.
The military leadership will insist on a bi-lingual DINFOS for two main reasons.
First: An all-English presentation of the military story will be insufficient against the contrary stories from a native Spanish-speaking opponent, with a direct
language link to the increasingly Spanish-speaking American audience.
That increasingly important civilian audience will take its information in Spanish from wherever it can get it. If the story that the military wants to tell is not told in Spanish then the news this audience gets will be missing the news that the American military wants to share.
Second: At first, and during a short conflict, contractors will handle the Spanish messages. When a quick military resolution does not come, the expense of this will be too great to source out and will be brought in-house, that is, to DINFOS.
(Perhaps, Spanish-speaking Defense Language Institute personnel will begin to meld with DINFOS personnel.)
Bi-lingual DINFOS personnel will receive bonuses, get greater training and advance quicker because of the situation.