It will never happen, not enough money or status and he doesn't actually want to play football that much. Apparently the Vikings tried to refer him to coaches of other teams in Europe but Brock never bothered to try contact them. He'd have to move, accept a money offer under 100k, work hard to even attain the level of the European league, probably have to sell his jet and estates in the USA... so, never it is.
But playing football is his "dream", that's why he left a million dollar WWE contract.
I think you are confusing "dream" with "excuse to stop touring endlessly because he missed his daughter".
So that's Brock's new excuse this week for quitting WWE? I can't wait to see next week's excuse.