Well we know for sure that Ada Wong gets an entire campaign for herself, so that should be enough to get you to buy the game if you like her character. She's also almost certainly going to be in mercenaries because there's no way they'd give her a campaign but exclude her from mercenaries.
you know what, i would agree with you. that if she has her own campain, it would be so strange if they don't include her in the Mercenaries aspect, would be nice if she can be also in the other multiplayer mode "Verses" as it has been confirmed (the "Slayers/Team Slayers" and the "Survivors/Team Survivors" mode and i'm well aware of the other modes later to be added as DLCs)
also when i do get the game and do the story, i can at least settle to be Helena (on Leon's part), Sherry (on Jake's part), Then on the Chris and Piers part, i may have to go with choosing Chris. As i assume you get to choose which character to be on each of the story (from the looks of what i've seen on the Resident Evil.net site)
*Since i have heavily stated that, i like to play characters of my gender*
So.... in conclusion, i have a Legit Steady-Positive (aspect) of this game and also a Legit Steady-Positive of getting it. Oh what the hey, "i'm going to throw caution in the wind" and get this, i have a feeling Ada will be an available character on the Multiplayer aspect of this (be it unlocking her, by doing the story and or her character being available to be purchased with "Set Amount of Points")
Side-Note: on the positive note, i have a 3-Month Subscription to Xbox Live Gold which will give me enough time to enjoy the campain, score massive points and have enough, to also enjoy the Multiplayer aspect part of the game,
So.....End of the World here i Come.