We may have seen the last of George John in a FC Dallas uniform. FCD confirmed yesterday (via twitter) that John left US National Team camp to go to Europe and explore a transfer option. While his agent had previously indicated a transfer this winter was unlikely, John would not have flow across the pond if a move wasn't in the final stages.
John has been looking for a move to Europe for some time, frequently turning down long term contract offers from FC Dallas. Clearly he can make a whole lot more money playing in Europe as Dallas (and MLS) can't afford to break their wage structure to accommodate John.
Given he will probably earn in England what would be a Designated Player salary here in MLS, it's a forgone conclusion John is gone eventually. It will benefit the club to transfer John sometimes this season, when they will get a piece of the transfer fee, rather than letting him leave for free when his contract runs out.
With the signing of Colombian defender Hernan Pertuz, Dallas has some cover in the back but will now almost certainly seek another center back via sign/trade/or draft.