10 Dec, 12:23
Ireland's John Lacey will referee his first ever RBS 6 Nations match in February, while Alain Rolland is also included in the Elite Panel in what is his last season.
Smith is returning to New Zealand to become part of Graham Henry's All Black coaching team with Wales coach Steve Hansen.
Solomons will bring with him forwards coach Adrian Kennedy when his three-year spell with Ulster ends at the end of May.
The 54-year-old former defence lawyer from Cape Town arrived in the province when Ulster were in the doldrums but in a short space of time he turned around their fortunes.
The former Springbok assistant coach guided Ulster to inaugural Celtic Cup success in December and they currently lead the Celtic League.
"There has been much speculation concerning Wayne's future at the club and we are now in the position to confirm he will be returning to New Zealand at the end of the season," Northampton operations director John Steele said
Smith said: "This is a special club with extraordinary fans and a great group of players. I will never forget my time here. My accepting this new role in no way undervalues how much Saints means to me.
"However, I love the All Blacks. I have been striving to play for them or coach them for a large part of my life. They have asked me to go back and the fact is I cannot contribute from here.
"I have a good relationship with Graham Henry and Steve Hansen. The prospect of working together for New Zealand rugby excites me."