My opinion only,
Basing will only be offered on A380 as it will have dedicated routes , the 777 and A330 often mix flights on the same sectors.
I guess new joiners will be offered a base on new t & Cs possibly not on the seniority list . Also the current EK pilots wanting a base would have to resign and rejoin possibly losing their 13 step salary and staff travel priority. Ie treated as a new joiner. If it is so popular will Captains be able to apply for bases as F/Os and wait. Im sure it can work ....
The 747-800 freighters will also be crewed into basings from outside probably with guys already typed on the -400.