A LEGO Technic Porsche Taycan should be available sometime in 2020.
That's if LEGO shows any serious interest in the Taycan, which in that case, a launch this year would be well within the typical development timeline i've seen from them.
So far Technic Porsche's like the 911 GT3 RS (42056), 911 RSR Racecar (42096) and the 918 Spyder (75910) should keep most of us Lego fans busy.
I still can't get over the life-sized (WORKING) Chiron they built