Canadian Tamron lenses distributor Amplis Foto has reported the availability of fast walk-around zoom Tamron 17-50mm F2.8 Di-II for Pentax K-mount:
Pentax owners will now have access to the 17-50 f/2.8 lens for Pentax DSLR cameras. The SP AF17-50mm F/2.8 XR Di II LD Aspherical [IF] is a lightweight, compact, fast standard zoom lens designed exclusively for digital SLR cameras. Exclusively designed for digital SLR cameras, this lens is a fast standard zoom lens that covers virtually the same angles as focal lengths of 26-78mm when converted to a 35mm format. The wideangle focal length is established at 17mm (26mm equivalent) to obtain a wider angle of view than ordinary standard zoom lenses, while maintaining the remarkably lightweight and compact size of the earlier full frame zoom lens model.
It could be pretty nice and almost twice cheaper substitute to the Pentax DA* 16-50mm F2.8 for all those who considering fast and wide "kit" lens.
Though, Tamron 17-50mm F2.8 doesn't weatherproofed.