The 21-year-old, who can also play across the midfield, failed to make an appearance in a Cherries shirt after signing last summer on a free transfer.
Released by Cardiff 12 months ago, the Welshman went on to have a successful loan spell at AFC Wimbledon, scoring one goal in 26 appearances.
The Dons were keen on snapping him up - but he now looks set to seal a move to Oxford United.
"Jon did very well during his loan spell with Wimbledon," manager Eddie Howe told the club's official website.
"We would love to be in a position to keep everybody but, unfortunately, we can't.
"We can't carry too big a squad and we need players who are going to be able to step in and play in the Championship.
"We need to create room for potential new signings and the agreement with Jon was reached with that in mind."