I'm not sure WTA pulls in great numbers on BT Sport - especially in those weeks when the action is half way round the world - but it will leave a gaping hole in the schedules week in week out.
At the end of the day, if you're a tennis fan you're going to go looking for the coverage anyway outside of Wimbledon so it doesn't really matter where it is because people will find it.
Improvements have been to Prime's ATP coverage since last year and having both tours in the same place is brilliant especially when it comes to combined events, and they will presumably have the multi-court coverage at WTA events that in the end never came to fruition on BT.
It'll be interesting to see if BT keep up their commitment to WTA in its final few months or if we will start to see more reliance on world feed commentary and perhaps not sending a team out to Shenzhen for the Finals as they have done to Singapore in the past.
Remember when Sky lost ATP that Mark Petchey left before their coverage ended and now he's a regular voice on Prime.
WTA tennis also probably leans female in audience (unlike a lot of sport) which is not as advertiser friendly (As female audiences are easier to reach)