2011 Cadillac SRXEnlarge Photo
GM Inside News now has additional detail, and cites a “source familiar with the program” as saying that the cancellation was due to battery inefficiencies. Specifically, the batteries used in the SRX plug-in hybrid were not seeing the efficiency gains that GM engineers expected, which likely translates to an unacceptable range on battery power alone. The same reasoning led to last year's cancellation of the Cadillac XTS hybrid.
It turns out that this isn’t necessarily bad news, since GM is working on a new hybrid system set to replace their older design by the 2015 model year. The new two-mode system is said to borrow from the Volt’s Voltec system, although GM Inside News didn’t provide additional details on what Volt technology may be implemented. While this doesn’t necessarily mean that a Cadillac SRX plug-in hybrid is back on the table, it does mean that the option for one may still exist.
Update: Green Car Reports has spoken to their inside source at GM, who says the real issues behind the cancellation of the SRX plug-in hybrid are more complex than just battery range or production costs, as previously reported. John Voelcker's report covers the situation in detail, but it ultimately came down to a mixture of production cost, unimpressive fuel economy and loss of a product champion within the GM organization. As with most things, the full story is often more complicated that it initially seems.