The problem with Revell is licensing. Lufthansa have a very close relationship with Revell and have asked them to create kits, for example the Fanhansa and the A380. You would of thought airlines would jump at the chance of advertising but as with everything in this capitalist worldk is theres a price and sometimes Revell won't pay it which is why we don't see many kits.
If you look at discounted kits then you can see a varied livery schemes. We will see more none German schemes in the future but they are more likely to be produced.
Concerning the B777, Lufthansa have 5 of the freighter version operated by Lufthansa Cargo. Now they have order 34 of the 7779-Xs which is a milestone move for Lufthansa. Now I can guarantee within the next two years max that Revell will release such a kit.