Highest ranked DMA's without an NFL franchise: (
Link)
Rank Designated Market Area (DMA) TV Households % of US
2 Los Angeles, CA 5,666,900 4.889
19 Orlando-Daytona Beach-Melbourne, FL 1,453,120 1.254
20 Sacramento-Stockton-Modesto, CA 1,409,400 1.216
22 Portland, OR 1,197,780 1.033
25 Raleigh-Durham (Fayetteville), NC 1,131,310 0.976
30 Hartford and New Haven, CT 1,018,770 0.879
32 Salt Lake City, UT 953,950 0.823
34 Columbus, OH 915,950 0.790
36 Greenville-Spartanburg, SC-Asheville, NC-Anderson,SC 878,550 0.758
37 San Antonio, TX 844,910 0.729
38 West Palm Beach-Ft. Pierce, FL 773,890 0.668
39 Harrisburg-Lancaster-Lebanon-York, PA 749,020 0.646
40 Birmingham (Anniston and Tuscaloosa), AL 747,190 0.645
41 Grand Rapids-Kalamazoo-Battle Creek, MI 740,230 0.639
42 Las Vegas, NV 718,030 0.620
43 Norfolk-Portsmouth-Newport News, VA 716,050 0.618
44 Austin, TX 707,430 0.610
45 Oklahoma City, OK 704,670 0.608
46 Albuquerque-Santa Fe, NM 703,720 0.607
47 Greensboro-High Point-Winston Salem, NC 699,040 0.603
48 Memphis, TN 693,860 0.599
50 Louisville, KY 674,940 0.582
(For point of reference, Jax is 49, Buffalo is 51, New Orleans is 52, Green Bay is 71)
Based on this, the only areas I would consider for expansion/relocation are Los Angeles and Portland. The other ones are either too small or too close geographically to existing teams (i.e. Orlando, Sacramento, etc).