That's my thought too but the trick is what do you do with it? It can't be as complex as a custom as you still need it streamlined and priced right for it to work.
The only way that I see this happening is if they completely dispose of the center bot. Then they could add two new figures that combine into the torso. However that is still rather lame given the clones limbs so they would have to be heavily upgraded or add at least two extra bots making them 4 new figures in total.
If it reaches a point in which 4 new bots make up the upgrade, then they may as well create a scratch built combiner as that would produce a better toy since they don't have to compensate for the flaws of the base figure.
As Lord_Zed said, it is possible that they could just produce a Crossfire 1 (Superion) type upgrade which just upgrades the figure by giving it a new head, hands and feet but that would feel rather short, specially after Bruticus. However I am still thinking that Crossfire 3 is the Glacier bot set.