Guile's trailer confirms SF6 is trying to leave no Street Fighter fan behind.
We already knew the parry was returning from SFIII. We knew Focus Attack and FADC analogs were returning from SFIV.
But now we have confirmation that SF6 is not abandoning SFV. Every character so far has V-Skill style special moves (Ryu's denjin charge, Chun's stance switch, Luke's Suppressor, Jamie's drinks). Guile literally has his VS1 in SF6. We know level two Super Arts can be used to function as V-Trigger installs. Guile's level 2 is his VT1. Most tellingly, we see a Crush Counter style counter-hit effect when Guile punishes a DP.
True, we already knew V-Reversals were also back as Drive Reversals, but many people were quick to attribute this to the Alpha Counter. No, this game is stressing continuity. It's not quite Smash Ultimate where "Everybody is here!" but every system is here.