Due to some stock dealings recently, Toyota now holds just over 20% of Subaru's stock. As the two companies grow closer together, we can expect more platform and engineering sharing to happen. Case in point, the next WRX.
The next WRX is still a few years away, however, Toyota and Subaru are already collaborating together on a shared platform the WRX would use. There is also a rumor that the pair are working on something new called "Super AWD", but it doesn't go into detail as to what the technology would be.
There is also the possibility of an AWD compact sports coupe that would have the same performance level as the WRX STI. The current STI is fading out in Japan where production ends in December with the EJ20 Final Edition. The WRX STI runs with a turbocharged 2.0-liter 4-cylinder that makes 304 horsepower and 311 lb.-ft of torque.