Can see him going back to West Ham as a replacement for Mark Noble. He's West Ham through and through, and they've played plenty of games this season between the league and all the cups so will fancy himself to get enough game time. The nice bump in wages and European football helps too.
Most of the clubs named are probably looking at him as a cheap homegrown squad option too. Burnley, Norwich, Fulham, and Sheffield United are the teams he'd have the best chance of getting into the starting XI.
At 26 this is probably the best contract he'll likely get in his career so don't blame him to take the best offer he can get and fight for a place at someone like West Ham or Wolves we'll say, and if it doesn't work out he can always move on in three years and probably still start for a yo-yo club like Norwich, Fulham, or Burnley depending on how they progress after relegation.
When he does move on would love to see Conor Coventry as a possible replacement for him at Anderlecht. Similar player to Cullen and playing for a top team in Belgium would allow him to showcase his talent like he is at MK rather than slogging it out in the bottom half of the championship. Could do wonders for his career like it has for Cullen.