I have said this before and I'll say it again SEGA is a company, they want to make money. They know they have a fanbase itching for a select few games, and they are going to deliver. Eventually. They are waiting for something, either a good idea for sequels for all the wanted games, one of them, or maybe they are releasing a console, who cares. Eventually we will get our Shenmue 3 and Jet Set Radio Next, Space Channel 3 and Chu Chu Rocket! 2, so I'm fine with sitting quitely and waiting.
TL;DR, don't fret, lad, your sequels are on their way~!
My words are the most powerful force in the universe! - Hideyuki from Bazooka Cafe