Yes, if you purchase the no expiration option, but it is not a good use of your money. Adding expiration to a 5-day ticket costs 77.75 with tax - almost the cost of the one day ticket you would have left.
A better play would be to book your package with one day tickets (if you have to book a package at all - e.g., you want the dining plan). Save the one day ticket from your package to use in January - it can be upgraded to the number of days you want, and it doesn't expire until you use it. You can have it removed from the Key To The World card (your room key) or leave it on and just bring the key back on your next trip.
For your October trip, redeem your GAD voucher for a one-day ticket, then upgrade it to a 5-day MYW ticket. You will receive credit for the one day ticket ($79 plus tax), so your 5-day ticket would cost 158.68. You would have already paid $79 plus tax for your package tickets, so your total cost would be the same, but you would have a one-day ticket left that you could use and/or upgrade in January.
A four day base MYW ticket is $239.63 for adults, including tax. A 5-day MYW base ticket is $242.82. Upgrading the GAD ticket gives you much more for your money since you get credit for the first day ($84.14).
If you are not planning to book the dining plan, you can book a room only reservation with Disney and upgrade your GAD voucher to the number of tickets you need. But if you want dining, you need to buy at least a one-day ticket.
