Some 6,000 Panther Valley miners idle over a seniority dispute may not return to work before Monday. President Mark F. Brennan of District 7, United Mine Workers of America, said no meeting is scheduled today with officials of the Lehigh Navigation Coal Company. The dispute involved the transfer of a man from the Lansford No. 9 to No. 6 colliery. Two-thousand miners walked out on Monday and the remaining workers Tuesday.