Great points, Centrale.
I wanted to add my own thoughts, I'd love another Panzer Dragoon or JSR, however I know SEGA well enough to not expect it any time soon (or ever). Not because I'm negative over why I'll probably never see sequels to those franchises, but because it just doesn't fit SEGA's m.o. Sure they have certain legacy franchises, but unlike Nintendo they don't use games like that as much. I mean, off the top of my head I can think of Sonic, Virtua Fighter and Phantasy Star as IPs that span console generations and have numerous titles up to today.
But, of course, then there are other IPs that are very strong for a brief period of time, and then fizzle out either due to devs leaving the company, or SEGA simply exhausting the franchise or moving onto something new. Alex Kidd, for example, was strong for a five year window. Panzer Dragoon was a four year window, and then we had a resurgence by way of Panzer Dragoon Orta.
So SEGA has surprised us once in a while with a long awaited sequel, but it is far from a common occurrence, and as such it isn't a strong expectation I have for the company. I'll still request my favorite IPs if SEGA asks, but I'm not going to expect another Shenmue or JSR every time they tease a new title.
PSO2 was this generations Panzer Dragoon Orta for me. I had never expected another title as big as what was revealed, and it was an awesome surprise. I'd say the return of Classic Sonic is another big comeback this gen.