In March, Microsoft turned heads when it publicly invited other platform holders, including potentially Sony, to have their online games connect to Xbox Live. Never before has there been cross-play between Xbox Live and PlayStation Network. While Sony did respond to Microsoft's invitation, the company's statement was indecisive.

Now, Xbox co-creator Ed Fries has called on Sony to respond to Microsoft's invitation in a more official capacity. This came up in an IGN interview in which Fries--who no longer works at Microsoft--talked about the "great job" Xbox boss Phil Spencer is doing.

"When I decided to quit Microsoft, I had 1,200 people working for me. One person walked into my office and said, 'Should I quit, too?' That was Phil Spencer," he said.

Spencer is a "great guy" who has a "ton of loyalty" to Microsoft, Fries added. Spencer, who was originally recruited by Fries, has worked for Microsoft for more than 25 years.

Fries went on to say that Spencer has done a great job of "fixing" some of the problems related to Microsoft's Xbox One unveiling and initial launch.

"A great example is this opening of Xbox Live for cross-platform play," Fries said. "I hope that Sony is going to respond. It's good to see some of the war kind of ramping down; more respect and cooperation between those two groups."

"I'm very optimistic for the future of both companies."

There have been no Xbox One/PS4 cross-play games yet, but Psyonix's soccer-with-cars game Rocket League could be the first, if it's ever allowed. Psyonix said it's not a technical matter holding it back, but rather it's an issue of politics.

"The only thing we have to do now is sort of find out where we stand politically with everyone, and then it's full steam ahead to finish the solution that we've already started," the developer said.