It's nearly the end of an era, as later this year Porsche will be lifting the wraps off the new 992-generation 911. While a new model is just around the corner, you can bet Porsche will keep rolling out special edition versions of the current 991-generation model for as long as it can. Our spies recently caught what looked like a new 911 Speedster prototype undergoing testing, which is rumored to make its public debut at this year's Goodwood Festival of Speed as a swansong to the current 911.

Details are scarce, but sources suggest it will be limited to 1,948 examples to mark Porsche's 70th anniversary since the automaker's first 356 sports car launched in 1948. But that may not be the only surprise Porsche has in store. Intriguingly, our spy photographers have spotted two new prototypes that appear to be convertible versions of the 911 GT3 touring. Changes are most noticeable at the back, where the prototypes bear a strong resemblance to the 911 GT3 Touring. A GT3 Touring convertible would certainly be unexpected, but it isn't entirely unfeasible. After all, Lamborghini now makes a topless version of the hardcore Huracan Performante.

Plus, there's a good chance the upcoming 911 Speedster has already sold out, so Porsche could make more money by offering a convertible version to customers who missed out on the Speedster. The GT3 Touring Package is essentially a spiritual successor to the 911 R, featuring a purist-pleasing six-speed manual, adaptive spoiler and a naturally aspirated 4.0-liter flat-six with 500 hp and 339 lb-ft of torque. 0-62 mph time takes 3.8 seconds before the GT3 Touring tops out at 196 mph. Of course, we could just be looking at a more production-ready version of the Speedster prototype spotted last week.

Either way, we should find out what Porsche has been cooking up before the next-generation 911 is unveiled at Paris in October.