[plt-scheme] v4 language levels

Right now, v3.99.0.9 has two separate methods for choosing a language:
the old way (the Choose Language menu), and the new way (#lang). So, a
few questions:

1. Are these two mechanisms going to be reconciled when v4 is released?

2. Is the old language<%> interface sticking around, or going away?

3. Will there be a way for students to use teaching languages without
having to use #lang?

4. Is there (or will there be) a guide on porting languages from the
old style to the new style?

5. Is any of this worth worrying about now, or might this all change in
unknown ways before v4 is released?

Thanks!
~ Aleks