If I were Scotland I would wait until after the UK exits the EU - the EU has already made it clear that Scotland has to leave with the UK, then possibly leave the UK and rejoin the EU. If, once exit is completed, the Scots feel they want to leave the UK they should have that option, but not before. Holding a Referendum next year will divert a lot of political resources from the EU exit to the Referendum and if Scotland DOES leave the UK it will find itself outside both the UK and EU - without any trade relationship with either.
The Scottish position is somewhat childish at the moment anyway, trying to cling to the doorframe whilst the rest of the UK tries to drag them to the exit. What's moor, it's foolhardy. If Scotland insists on holding a Referendum on leaving the UK so that it can remain in the EU what happens to those parts of Scotland (and there likely will be some) that vote to remain part of the UK? Will Scotland try to drag those parts out of the UK like it is being dragged out of the EU?
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