G Dustin Wolf
No matter what the Flames do in net this summer, Jacob Markstrom has just two years left on his current deal, so whether he sees that out or not, he won't be in net for the Flames when the rebuild begins, but the answer could be right in front of them already. While people have very reasonable questions over Wolf's size in net, he has shown in the AHL that he's capable of being a dominant goaltender, and now it's all about adjusting to the game at the NHL level, which routinely takes time for goaltenders.
At 22-years of age, Wolf has done all he can in the AHL, and has been solid in 15 appearances for the Flames, tallying a 3.03 GAA and a .909 save percentage, and with his athleticism, confidence, preparation and likeability, he needs to be in net for the Flames long-term. Sure, it's going to take plenty of time, and it may be very ugly over the next few years, but if the Flames can keep building him up, he will be 25 when the new arena opens and in perfect position to solidify himself as one of the top goaltenders in the NHL.