You may get a spawn from both as they will try to fill the pond if possible. In addition you may get some growth and those fish will be there ready to spawn first next spring. Plus you will have fish there and not be dependant on supply and timing next spring. Further in the spring what you can buy will probably be yoy (hatchery not going to sell you its brood stock). The result is those put in now will spawn way before next spring's additions will. So you will have an extra spawn class and size. You may lose some to cold and predation but the risk is small in view of the potential extra fish, the time gained and risk that you can't get them when you want them.