I can see this happening. Toward the end of the season Brawn had lost its edge over the competition and the two top teams were Red Bull and McLaren. That's one reason why Button left for McLaren. With Rubens gone as well, Brawn will need some serious driving talent to compete this year. Ross Brawn and Schumi are one hell of a team, so it all makes sense. The two things standing in the way are the condition of Schumi's neck (which is a huge issue) and the condition of Schumi's marriage (which is probably less of an issue to him).
I can't wait for next season if this proves true. We'll have four former GP champs and one future GP champ all in competitive machines. Should be awesome to watch.