I definitely agree. The biggest argument for them to bring back the western theme is right here:
They didn't have a cow before, and that was a glaring absence in the earlier western sets. They've also got other new elements they could include, like the Indiana Jones hat, that could add some diversity to the previous molds. The Wonder Woman lasso from the upcoming Super Heroes line is another element they could include.
I've argued this before, but I felt like they missed out on having a third year of the theme that focused on civilian life:
Impulse set - Cattle rancher - cow, cowboy, lasso (this would be an obvious 'army builder' set as people would buy large quantities to get a herd.
Small set - Settlers - Ma, Pa, kid, covered wagon
Medium set - Homestead farm - same family, small house, shed, cow, chicken some farming implements (think of some parts of Mill Village Raid brought forward to the late 1800's)
Larger set - general store
Biggest set - town
Of course they could sprinkle in some 'bandits' or 'injuns' if they really need to make action.
Then they could also cross theme with having a railroad tie in with the steam engine and a couple of car designs as separate sets (of course one would have to be a cattle car). Then a western-themed train depot would be an obvious set as well.
Final point - girls. There is often a discussion of how to build in appeal to girls. My wife has gotten hooked again lately into watching all of the Little House series (it runs a couple of times a day on the Hallmark channel, so we DVR it and watch it at night). Of course these books and the show have been family favorites for decades, and especially with girls since the main protagonist is Laura. These show that a western theme that is not just about gunfights and Indian raids could connect very well with girls. For set designs just take a look around Walnut Grove - the Olsen's store, the mill, the schoolhouse/church, farms etc.