I totally disagree. San Antonio has been annexing property in the South, NW, and North periodically for the past several years and more plans are in place. Example: Stone Oak was annexed in 1998. Stone Oak is substantial and continues to add people and homes. The Braun Rd, Shanefield Rd area outside of 1604 is bit by bit being annexed by The City of SA.
Check this out. As recently as 2002 in the south and small parts of north and nw for just one year.
http://www.sanantonio.gov/planning/study_areas_2002.pdf