You can read the body of the directive here: http://www.whitehouse.gov/news/releases/2007/05/20070509-12.html
I'll go through the directive and address the important points as I see them.
(2) In this directive: (e) "Enduring Constitutional Government," or "ECG," means a cooperative effort among the executive, legislative, and judicial branches of the Federal Government, coordinated by the President, as a matter of comity with respect to the legislative and judicial branches and with proper respect for the constitutional separation of powers among the branches, to preserve the constitutional framework under which the Nation is governed and the capability of all three branches of government to execute constitutional responsibilities and provide for orderly succession, appropriate transition of leadership, and interoperability and support of the National Essential Functions during a catastrophic emergency;This rather clearly states that proper Checks and Balances will remain in effect and that the law of the Constitution will remain, ensuring elections will still take place as laid out in Article II, section 1 of the US Constitution.
(11) Continuity requirements for the Executive Office of the President (EOP) and executive departments and agencies shall include the following: (b) Succession orders and pre-planned devolution of authorities that ensure the emergency delegation of authority must be planned and documented in advance in accordance with applicable law;
(20) This directive shall be implemented in a manner that is consistent with, and facilitates effective implementation of, provisions of the Constitution concerning succession to the Presidency or the exercise of its powers, and the Presidential Succession Act of 1947 (3 U.S.C. 19), with consultation of the Vice President and, as appropriate, others involved. Heads of executive departments and agencies shall ensure that appropriate support is available to the Vice President and others involved as necessary to be prepared at all times to implement those provisions.This also seems to clearly that state that powers shall be accorded in compliance with the directives listed in Article II, section 1 of the US Constitution, and in US Code Title 3, Chapter 1, Section 19 regarding the processes of election and succession.
(21) This directive: (c) Is not intended to, and does not, create any rights or benefits, substantive or procedural, enforceable at law or in equity by a party against the United States, its agencies, instrumentalities, or entities, its officers, employees, or agents, or any other person.This seems to clarify that no special powers or rights are granted by this directive and that it serves only as an organizational document to serve in expediting effective governance in compliance with the US Constitution and other applicable laws in a time of catastrophic crisis.
In summary, this is nothing to worry about.