There was a lot of talk about a 1.5 turbo BMW mill in the '19s.
Personally, I haven't heard such a specific rumor. Just that there might be a BMW engine, a rumor probably based on the fact that exchange of engines between BMW and Toyota, including Corolla, are not unusual for the European market. 1.5T would be nice for a niche/image engine but in the econobox compact segment, turbos are more often used to gain EPA mpg numbers with small engines that don't always translate in real life or performance.
I have never seen a car kept in secret as much as the next generation. That may be a very good sign.
Be patient
. That's quite normal marketing : calculated rumors, pseudo-leaked or spy pictures, pre-production model presentation... The car is still months away from being available in Europe, plus another year in North America. Old GM used to unveil details on models a couple of years in advance... only generating a "deja view" impression at launch. On the other hand FCA rushed the otherwise quite good Dart without having the complete line/options available, turning away forever a whole bunch of consumers. Creating a momentum is marketing art !
Now if they would only bring back rear wheel drive.
... But it won't happen with a mass market compact/practical car. Try a Cadillac ATS for a cramped interior... yet it shows the option exist, just not in models that sell 1 million+ every year.