My own view is that they will have to at the very least run their own referendum in 2020 and even if it isn't the trigger for a UDI declaration (in the event of a YES win) then it will be more leverage for a confirmatory referendum later and possibly the start of discussions on independence with the government.
I've been avoiding this thread (don't need the stress) but there's a point here that people are missing and to be frank most commentators in Scotland are missing too. It is probably impossible, in practical terms, for the Scottish government to hold a referendum without either a Section 30 order or a court finding that a Section 30 order is not required to do so.
The reason is that elections and referendums are run and administered by local authorities. They have the mechanisms, the infrastructure and so on. They are also all (or almost all) under the control of unionist parties. Even where the SNP won the majority of seats in the STV elections, unionist coalitions have been formed to prevent them being in administration. Labour seem happy to cosy up with the Tories to do this. If the Scottish government tries to call an independence referendum without a Section 30 order they will most certainly declare that this is illegal and refuse to co-operate. Then what?
The electoral system as run by the local authorities is secure. It's absolutely impossible to subvert on a systematic basis. We totally need it to run a fair and honest referendum. If the Scottish government thinks it can circumvent this and use a different system (maybe an all-postal vote based on the electoral register without using the councils?), it's going to have a great deal of difficulty persuading anyone that that is secure and not open to tampering.
Not only that, it's a dead certainty that the unionists will call for a boycott of this "illegal vote", so that unless there are more Yes votes than 50% of the total electorate if would be impossible to say there was an actual independence majority, even if Yes won the actial vote substantially.
Then where are we? Catalonia without the violence, that's where. And I'm not laying any large bets on the violence part either at that point.
The Scottish government should have applied to the court at least two yers ago for a ruling on the necessity for a Section 30 order. If it was ged unnecessary then all the above problems would go away, but without the ruling the unionists will insist that it's necessary. If it was judged to be necessary then we'd know where we stand and could work on other strategies.
As things stand it's simply an unholy mess.