Have you seen how the majority of the SOCOM community is over the franchise? SOCOM 4 is a piece of shit in the community's eyes because it changed too much and there's no way you'd expect them to be fine with a portable game that has NO multiplayer besides coop or not a dedicated campaign. It'd start up an even bigger shitstorm and it might just be worth it to have it as a new launch IP.
Personally, I see Unit 13 as an experiment of Zipper's to see what works and what doesn't on the Vita and to get their feet wet with the hardware so they can learn from this game and apply it to a SOCOM game in the future. FTB4 would be an AWESOME announcement since the previous games were good but the lack of a second stick limited them. Imagine a competitive SOCOM game on the go and it's enough to make any fan drool.
To call it a SOCOM game would require more content, especially competitive MP. I wouldn't have a problem with it but I think they did the right thing in not calling it that. Remember that MAG was once called a SOCOM game but they learned it was best not to call it that either, lol.
The SOCOM community is damn crazy and I think I lose my sanity when I'm on the game's forum to the point where I stopped posting. Hell, 3 of my clanmates were one of the 18 to be the first people outside of Zipper to play SOCOM 4's MP and we always had a big presence but that place drove us away basically. I just wish they had more S4 DLC to keep us going.
Unit 13 |OT| It's SOCOM but not SOCOM