A more scalable solution that doesn't require serialization is this:

CREATE PROCEDURE [dbo].[uspGetNextID]
(
  @inID BIGINT OUT
)
AS
      SET NOCOUNT ON
      INSERT INTO SequenceTable DEFAULT VALUES -- Empty table with an IDENTITY column;
      DELETE FROM SequenceTable WITH (READPAST);
      SET @inID = SCOPE_IDENTITY();
RETURN;

A more scalable solution that doesn't require serialization is this:

CREATE PROCEDURE [dbo].[uspGetNextID]
(
  @inID BIGINT OUT
)
AS
      SET NOCOUNT ON
      SET IDENTITY_INSERT SequenceTable ON;
      INSERT INTO SequenceTable (id) VALUES (@inID);
      SET IDENTITY_INSERT SequenceTable OFF;
      INSERT INTO SequenceTable DEFAULT VALUES;
      DELETE FROM SequenceTable WITH (READPAST);
      SET @inID = SCOPE_IDENTITY();
RETURN;