It's easily doable and yes you are right, a whole new landscapes in January.
One can easily go till Sost via Karakoram Highway, Khunjerab Pass won't be accessible.
Skardu Road is different, it can be block due to heavy rainfall/snow, but there's active teams for this purpose so don't take long to reopen, you can easily go to Skardu, Shigar, Khaplu.