As the so-called flagship of the Cadillac sedan lineup, the STS will soon be replaced by an all-new and significantly more updated model. At the moment, Cadillac isn't saying much about the new model, but it's likely that it'll RWD drive of the current STS. Since the replacement depends on developmental money, the current STS remains in place for now. And even though its age is showing, it remains competitive for those who want a powerful rear-drive large sedan.
It's still competitive against the European and Asian imports with a long list of standard features and available all-wheel drive. The STS-V high performance model is no longer available, so that leaves the CTS-V as Cadillac's sole supercharged offering, for now. In the future, you can likely expect for the STS and DTS models to be combined into a single large rear-drive model that will probably be built off an all-new large car platform GM is currently developing.