Guild Wars 2

“With the holiday season at an end, the last remaining Wintersday merchant is closing shop. Make sure to finish your exchanges before January 28th PST, when the Festive Lionguard will be packing his wares and leaving Tyria.”

My question:
Will the Mystic Forge recipes for wintersday items stay? (ex: recipe to make Endless Plush Griffon Tonic)
Or is this only referring to the vendor that sells wintersday items for ugly wool sweaters/socks/hats?

They just mean the vendors. You can still use the Mystic Forge for the items as long as you have the materials. Works the same way with the Halloween stuff.