I've just posted on the Scotland Forum the new restrictions coming into force from Boxing Day on crowd size and the banning of Edinburgh's Hogmanay celebrations and other restrictions.
https://community.ricksteves.com/travel-forum/scotland/hogmanay-cancelled-and-other-restrictions
As far as travelling up there, train companies have started cancelling trains all over the UK because of covid related staff shortages.
Plan carefully, plan very carefully...
More England restrictions are on the way, just not made public just yet