Tex. Local Government Code § 43.127

(a) Except as provided by Section 43.123(e), on or before the date prescribed by the regulatory plan under Section 43.123(d)(2), the municipality must annex the area for full purposes. This requirement may be waived and the date for full-purpose annexation postponed by written agreement between the municipality and a majority of the affected landowners. A written agreement to waive the municipality's obligation to annex the area for full purposes binds all future owners of land annexed for limited purposes pursuant to that waiver.

(b) In each of the three years for which an area may be annexed for limited purposes, the municipality must take the steps prescribed by this subsection toward the full-purpose annexation of the area. By the end of the first year after the date an area is annexed for limited purposes, the municipality must develop a land use and intensity plan as a basis for services and capital improvements projects planning. By the end of the second year after that date, the municipality must include the area in the municipality's long-range financial forecast and in the municipality's program to identify future capital improvements projects. By the end of the third year after that date, the municipality must include in its adopted capital improvements program the projects intended to serve the area and must identify potential sources of funding for capital improvements.