We knew a Porsche pack was coming eventually but the new track is a bit of a surprise. Somewhat gives me hope that they'll eventually release a new pack with some of the older original tracks from the previous games in the series.
20 would be quite disappointing as it's not nearly enough to cover a manufacturer with such heritage and history. It's also strange because BADNED had mentioned in the past that there would be more Porsche than in the Expansion Pack from FM4.
Also, "only" 9 brand new to Xbox One from the 20. this means, we'd either be loosing one of Horizon's Porsche or one is getting updated to a newer spec (my bet would be on the later with the Cayman being upgraded to the GT4 spec)
The 919 and 356 would be two of those 9 brand new. I suppose we'd see the return of the 962, 911 GT1, 550 Spyder, at least one 911 (991) RSR. That would already leave only two spots for new-to-Xbox One models. Surely, they have to be the 917 and 935 with the focus on Can-Am and Group 5 we've seen in the game...