This feature most likely will not make it in, as we are trying to get WPF Studio 5.0 out in the next couple of days.
There are some additional cases we need to work out before implementing this feature. In your example, what is considered a "literal" is easy to identify. Since our mask supports a simple regular expression there can be things like "(1\d|2\d)". In that case, the "1" and "2" are technically literals, but are required in order to choose the correct branch. What are your thoughts on this case?
Keep in mind that there can be hidden "branches". So in your example, if you had "###?.###.###-##", then again the "." is a literal but would be needed to choose the "branch" that only requires 2 digits before the first ".".