It originally seemed that Brek Shea would be returning to MLS and Toronto specifically, but now with that move out of the way because the two sides couldn't come to terms Brek Shea will certainly be pursued by several clubs and many of them in MLS. Shea is currently training with FC Dallas his former club, and a move may be in order, but several scenarios would have to fall in place first.
Shea signed with English Premier League Side Stoke City from FC Dallas on transfer deadline day (January 31st) in 2013 after a long negotiation period that seemed to die out several times. Unfortunately this deal has not turned out well for either side and Shea has only seen action in 3 matches with none of them being starts. This resulted in Shea being loaned out to Barnsley F.C. in the English Championship (second division) on a short loan that was cut even shorter when he was caught in a rather silly debacle that saw the club release Shea. Needless to say his time since leaving FCD in 2013 has not turned out as foreseen.
FC Dallas currently has a full roster with 30 players and it is assumed that the management has formed the roster to where there is very little cap space left to be spent. This means the squad would likely have to move one player, if not more, to make room for Shea to hop into a roster spot. This is also assuming he is not demanding a DP contract, which FCD could not accommodate while they already have 3 young designated players on the roster (only 3 spots are allowed.)
Shea will likely enter through the "Allocation Order" and FCD is currently 3rd on the list behind Toronto and Columbus and would have to make a deal in order to move in front of both of those teams which would cost the club a large chunk of change and that is even before signing the player himself. MLS will do almost anything to help a club sign a player as long as both parties are in agreement, so having MLS' approval on this matter may help FCD move forward if they plan to do so.
Also, you must remember that Shea did not necessarily leave the club on the best of terms after a rough year. Shea was limited in his playing time after injury problems and an altercation with then Head Coach Schellas Hyndman and was sent home from practice and left off several matchday rosters. I would imagine most, if not all, of these problems are old news now that Hyndman has moved on, but there's no telling how the club views this situation now.
Shea may be a native Texan, but this move seems very unlikely to happen given the scenarios it would take to come into fruition. Oscar Pareja has stated that he is happy with the current roster and I don't see him moving 1-2 guys that he trusts at this point to sign a player that hasn't seen the field too much in the past two years. All in all, it is a move that is very unlikely to happen, but one can always hope right?