The concept of a .45 acp Shield is not improbable. After all, during the time of the 3rd Gen. semi-autos, there were single stack full size .45's, compact .45's and the sub-compact (for that time) CS45. In addition, the CS 45 with Big Dog grips is approximately the same size as a G36. Like anything, they have to figure if the R&D, tooling, etc., will worthwhile with the amount of sales.
JMH $.02