Rumors have been floating around for a little while, but Ricoh (who owns Pentax) just put up a teaser website for a new full-frame DSLR. The only detail given is that the camera will be released in the spring of 2016.
People have guessed that the camera will contain either a Sony made 36 megapixel sensor (such as the one found in the Sony A7R and Nikon D810) or a Sony made 42 megapixel sensor (such as the one that's found in the Sony A7R II), but Pentax hasn't said anything yet.
Pentax has a few different unique innovations found in their DSLRs with APS-C sized sensors, and it is thought that this camera will also include those. One of those innovations is pixel-shift, where the camera takes three different exposures, but moves the sensor one pixel each time, allowing the full image to be captured in each color channel. This basically creates a faux Foveon effect, but it requires the use of a tripod and a perfectly still scene.
Pentax makes quality products, and it makes sense for them to jump into the full-frame game, since they make both APS-C DSLRs and medium-format DSLRs. They used to make 35mm SLRs.
The thing that's great about Pentax is that any k-mount lens is compatible--you're not stuck with a limited selection. If you don't mind manually focusing, great used prime lenses from the 1970's and 1980's can be had for almost nothing and they work great on that brand-new DSLR.
The challenge for Pentax will be pricing. If they price it the same as Nikon or Sony (or Canon) cameras that are similar, I don't think it will be all that successful. If they were smart they'd come in around $500 less so that the price will entice customers to buy Pentax instead. Or, perhaps, Pentax feels that enough of its existing customer base will "upgrade" to this camera that they can price it however they want.
Be careful to avoid G.A.S. because whatever camera you have is good enough as long as the photographer is good enough. A new camera will never make you a better photographer. Even if this new camera proves to be fantastic, the gap in image quality between it and, say, a four-year-old Pentax K-30 is going to be pretty small. It's difficult nowadays to find gear that's not at least sufficiently good.