Wow, everyone is thinking so big here :O
When they say 'end of the series like it is now' I was thinking of somekind of reboot.
Back to Stillwater, back to zero,... But then a totally new Stillwater, with hiqh quality graphic etc... and a lot of life. Helicopters and planes flying over the city, boats on the water, the trains or even subways and more life on the streets themselves. Customisation would be back at its top level, with completely customisable cribs, cars, gang, weapons,... and the option to use layered clothing. A large aresenal of weapons and a fuckton of different cars and some of those other cool features SR 2 had, like Fuzz and taking food/joints/drinks with you should be back.
And I would also bring back some of the sad moments SR2 had like that brotherhood mission involving Carlos or the scene where the Ronin fought the Saints in Aisha's house and things got out of hand,... Those really were moments that touched your feelings and made you hate the rival gangs more and more. The way how the Saints took care of Shogo must have been one of the best revenge scenes I've seen so far.
The map also could be bigger offcoarse and other cool vehicles could be added.
Thats my idea of how it could be rebooted. But everyone can has his own dreams about a next SR game
i was thinking a total remake of 2 with the upgrade system and combat of 3!