Data reference integrity after mass delete to tables with equence autonumber as primary key

Hi All:
If a table (e.g: 10+ millions rows) has "sequence number" as primary key (OID), then after perform a mass delete like 50% of its rows are gone, will the next OID  still consistently auto-increased from the last sequence number, or it went down together with deleted data since 50% of its data are deleted?

Suppose not exp/imp performed or anyother table shrnking methoded used after the mass-deletion.

e.g:  Table structure like below -

SQL> /
 Name                                                              Null?    Type
 ----------------------------------------------------------------- -------- --------------------------------------------
 ACTION_DATE                                               DATE
OID                                                               NOT NULL NUMBER
FINAL_REQ_STATE                                       varchar2(30)

OID is object of sequence and it is the primary key.