Well FFVII came out in 1997 and since them they haven´t let Cloud go.
Not at all the same thing. Cloud wasn't the main focus for FF for several years in a row after its release like for XIII even after the final game in the series. We had Squall and Zidane, no one talked about Cloud all the time. The reason Cloud is popular even still today has to do with his iconic presence. It's not just about sales but as the forefront for pushing FF into a new era of gaming and leaving a lasting impact on gamers.
Cloud is only mentioned when it comes to his game, not in random situations like random clothing line integrations. G-Bike was all about a game with Cloud in it, Cloud in Smash has to do with fan vote and also likely a cross collaboration with SE over the FFVII Remake which again is fan requested (and also has more than JUST Cloud in it). Name the last time you've seen Cloud promoted somewhere completely out of context in a situation like this... I can't think of a single one. It's okay to promote these FF characters, but doing so like this, and on such a sensitive character (a lot of people hate XIII and Lightning) the backlash from the community should be completely understood and acceptable honestly.
It seems like they are trying to promote Lightning in many areas to try and show that the XIII series wasn't a mistake honestly. She's being ham fisted into places where they don't make sense. I think if this was done more timely to a release of one of the XIII games, it would be more accepted in the community by people. The problem is, it's almost 2016 and the last XIII game released in 2013, and for some reason we are still getting random things from Lightning in a bizarre clothing collaboration? It just seems like they are ham-fisting Lightning into these different roles to try and promote her character as a way to spin positive PR towards the XIII series. Is it interesting? Sure, although I think the clothing looks really bad.
If this came out in conjunction with ANYTHING XIII related, at least it would make sense. Hell, if they even announced a PS4 port (which I do not want at all) I would be okay with this in conjunction with that. But this is completely misplaced and foreign to me and to many other people.
I'm sure the FFXV cast will get similar appearances over the next five years or so.
I really doubt that, they haven't done it with XIV at all, so why would they do it with anyone from XV? XV already has clothing tie in with Roen anyway, so I doubt they would do anything similar to this. At least Roen designed clothing specifically for these characters...
And no, it's not really a big deal, but people get confused as to why people just sort of groan and sigh at seeing things like this as if it's not obvious the second you see a video of Lightning swooping around wearing expensive designer clothing and holding out a handbag/clutch.