The problem with the Wankel was a lack of complete burn of the fuel and consequently, exhaust temperatures. An engineer did patent a fix for this by adopting an oval ejection port. This helped increase the burn time and reduced the exhaust temp.
My contacts tell me that Mazda has currently tabled the Wankel, but is investigating the patent. No word as to when or if they will adopt, bring back, etc.
Actually the RX-9 is in the works with an 16x wankel engine
http://www.motoring.com.au/mazda-rotary-details-firm-46719/