It was a small step for fighters and one giant leap for SF, thats for sure. It should be obvious that only SF has really returned to the mainstream, but it has ultimately spurned some interest in other fighters. If we consider the amount of people who picked up SF, it's safe to say that the great majority of them are "casual fans." Casual fans do not follow message boards such as this as regularly as us, they don't get all of the details on the game before buying it. It's safe to say, casual fans do not give a shit about netcode (enough to research it in advance, I'm sure no one is happy with T6s netcode.) I have a hard time believing that word spread to all of the casuals that T6 has shitty netcode, they probably just aren't interested in the series at all.
This is why I say a patch is not going to boost sales. Either they're not interested to begin with, or will not know about the patch, or will not think it is going to help anything due to what their friends are saying etc... The game is not going to suddenly explode in popularity due to a patch, it's very very unlikely.
EDIT: Namco does suck, they prove it time and time again. It doesn't stop me from enjoying Tekken though, they still made a good fighting engine. They aren't called Scamco for no reason at all though. SC4 is the last SC game I get due to the overall bad experience as well as the DLC characters, that was fucking ridiculous. To be perfectly honest, the quality of this upcoming patch will determine whether I get T7 or not too. I refuse to keep getting wallet raped by a big Japanese company that doesn't give two shits about me.