While I bet going the Batman Beyond route is more likey to happen,
is a win, win thing because there are so many opportunities for Warner's to make money and for the fans to get more Batman.
Just think, you can produce two
ongoing Batman film series. A contemporary Batman and then the future Batman of beyond. You don't even really have to worry about market saturation because they're two different characters (Wayne and McGinnis) in two different genres (noir and cyberpunk). In two different time periods. It would give Warner Brothers a license to print money.
Shit, even if one of the series is unsuccessful they can keep producing the other and we still got an extra Batman movie out of it.
How is it that they aren't doing this right now?