Why would anybody want Sideshow to lose this license
Because some long-standing members like trolling in sections where they have no real interest.
As for the Max Rebo Band, I think we've seen the Jabba's Palace offerings come and go. The impression I get is that Jabba wasn't the slam dunk Sideshow expected, so aside from main characters (Slave Leia, Lando Skiff), I don't think we'll see anymore background pieces.
A Landspeeder would be a very cool offering, and I imagine Sideshow will be looking at Hot Toys'
Dark Knight Tumbler and Batpod as an indicator of the market for such items--especially considering their close relationship with that company. If those succeed, Sideshow may be more willing to get their feet wet. However, they'd have to be very selective and choose vehicles that are iconic and/or likely to be popular.
It wouldn't surprise me if the first two such offerings from Sideshow are the Imperial Speeder Bike (not too far-fetched considering Hasbro mass produced one for $50...Sideshow could probably make a higher-end version for $200) and the Landspeeder. Both would not be space-hoggers and would be very attractive to collectors.
Getting back to the main figure line, the introduction of the Clonetrooper base body opens the floodgates for the Militaries of SW line to really take off. In the next year or so, I fully expect to see the following:
Clonetroopers (including paint variants)
Stormtrooper (and Shadow Stormtrooper)
Scout Trooper
Snowtrooper
Galactic Marine
Elite Corps Clonetrooper (Kashyyyk)
Boba Fett
Jango Fett
Commander Cody
Darth Vader (the version likely to be debuted at SDCC and at least one other variant within the next year)
Count Dooku
Of course, such releases would hopefully be spaced out considering their price would be $80 or higher.