Ok, since this is a "What If" scenario I'm taking for granted that we are looking for answers in the hypothetical realm.
So, hypothetically the 6 inch line fades from existence in 2010, your question is could another company pick the line up? It's already been mentioned that Marvel Select could pick the line up, since they have a deal outside of the current license agreement, which is the most likely scenario for the continuation of the 6 inch line.
Another hypothetical possibility is that the 3 ¾ inch line fails and Marvel revokes or buys out the remaining portion of the contract with Hasbro and begins to produce Marvel Legends again.
My last hypothetical scenario involves a renegotiation of the current agreement between Marvel and Hasbro that allows for Marvel Toys to produce a 6 inch Marvel legends line only (similar to the Marvel Select arrangement) while Hasbro maintains all other aspects of the current Marvel license which would allow them to continue with the marvel based Transformers, 3 ¾ inch figures, Marvel Potato Head and any thing else that they wrap their heads around.
There you have three "What If" scenarios based solely in the hypothetical realm.
In reality I don't think there is a snowball's chance in hell of any of these scenarios playing out, but you put it out there, so I answered. :spidey_read_thread: