No, open transactions are not commited by this statement. You can test this yourself:
create table TESTSWITCH(testid NUMBER);
insert into TESTSWITCH values(1);
select * from TESTSWITCH;
alter system switch logfile;
rollback;
select * from TESTSWITCH;
output:
table TESTSWITCH created. 1 rows inserted. TESTID ------ 1 system SWITCH altered. rollback complete. no rows selected