Yes as DK already said a datapump export is a logical backup so instead of you copying datafiles which contain blocks fomatted in the endianess of the operating system you are just copying files which contain a series of commands to recreate all the objects in the database. You can think of an export file as containing something like the following:
create tablespace xx;
create user xx;
create table xx;
insert into xx values (yy);
create index zz on xx;
So this file can be loaded into any platform - it doesn't care.
Let me just add that if you were to use the TRANSPORTABLE feature of Data Pump, then the endian issues would be something that you would have to worry about. In this case, you are copying data files from the source to the target and you would have to run the data files through RMAN to convert to the correct endian values. RMAN works as long as you don't have encrypted tablespaces or encrypted tables.
Hope this helps.