The Marlin actions now available are not suited to such rounds as the 30-06, 300 WSM, 308 Win., ect. That is why you see such rounds as the 308 & 338 Marlins. Winchester tried it before in the model 94 with the 307 Winchester in an effort to duplicate the tried and true 308 Win. In the long run it did not work, as is the case with most propriatery cartridges. It's hard to compete with established rounds.
If Marlin wants to go for high intensity modern rounds in a lever action, a new action is in order. The trick for Marlin is to come up with something that appeals with it's tradional customer base, while exciting those who like the lines and handeling of a lever action, but have been put off by the cardridge selection. These are the guys who flock to the Browning BLR, and buy a ton of em' in the traditional high power bottle neck calibers.
Me, I own both Marlins (44 mag & 45/70), as well as several BLR's, and they are totally different guns. I will be curious to see what Marlin comes up with. I would say they would be smart to stay with steel and walnut, and stay away from the weird styling we are starting to see on some new Browning models, for example. Maybe an updated, trimmer version of the Winchester 88? A more traditional tube fed gun with a spiral tube to prevent bullet tip to primer contact, so modern spitzers could be used? Does not have to be a front locker, could be a rear locker like the Winchester 86/71, only with modern steels to make it strong and reduce bulk? Lots of posibilities....

Larry