If Scotland leaves the UK there will never ve another Labour government.
I don't think that's going to make any difference at this point. Not for an exceptionally long time anyway. For now there's nobody in the Labour ranks capable of leading the party to an outright GE victory under any circumstances.
And, in case you'd forgotten, for the time being the Conservatives, Labour, and Lib Dems are all tied up in Scotland with one MP each.