Some new town homes could be in the works near Zion Presbyterian Church in Lansdale.   The redevelopment of 421 North Line Street has been proposed by W-B Homes.   A roofing and siding company used to operate on the one and a third acre lot but it is out of business and the property has become overgrown while the buildings there have fallen into disrepair.   W-B Homes already has a successful town home project underway on Cannon Avernue in the borough.   Plans for the Line Street development are only in the preliminary stage and at this point it is not known if the builder would need zoning relief before the project could move forward.