At some point, I'm sure MAME will be synced up with Supermodel. I'm not familiar enough with MAME (and lack the time) to work on it myself, but there's a reason why Supermodel is open source. MAME's Model 3 driver was based on the original Supermodel, by the way. Last time I checked there were still a couple of fragments of code in there taken verbatim from the first Supermodel
Bottom line: it's really all part the same effort, if you think about it.