The Order In Council proposed to amend Schedule 5 and permit the Scottish Parliament to legislate on the matter has not yet been passed.

The matter of the the Union remains legally an exclusive matter for the British Parliament

However

The Scottish Parliament’s recently set up Referendum (Scotland) Bill Committee has now voted to support the Edinburgh Agreement proposals to give the Scottish Parliament the power to hold a referendum on the Union.  This is now subject to a vote by the Scottish Parliament.