Yes, Cached sequence value will be lost , even if you do :alter system 
flush shared pool.

11:31:00 scott@O...> create sequence test_seq cache 1000;

Sequence created.

Elapsed: 00:00:00.02
13:52:55 scott@O...> select test_seq.nextval from dual;

   NEXTVAL
----------
         1
13:53:02 scott@O...> set autotrace off
13:53:07 scott@O...> alter system flush shared_pool;

System altered.

Elapsed: 00:00:00.01
13:53:13 scott@O...> select test_seq.nextval from dual;

   NEXTVAL
----------
      1001

Elapsed: 00:00:00.05 > finally i got the chance to look the sample 
chapters of your new book in beta today (interesting topics covered), 
another must to have book for all dba's :-) 

> okay, i was going through chap. 4 page 8 where you discuss about 
sequence being one of cause for 'recursive calls' and how to mitigate 
those calls. don't know what it might be worth of..."There is a chance due 
to shutting down,..." Sequences doesn't loose its cached value if the 
database are shutdown normal or immediate only on aborts seqeunce looses 
its cached value. not sure if you want to be that specific but thats my 2 
cents.

> once again thanks for yet another wonderful book and the service that 
you provide to dba's / developers through asktom.oracle.com 

> Stan