The FIA (or more specificaly, Max Mosely) has released a preliminary proposal for rules changes to take effect for the 2008 season:

FORMULA ONE WORLD CHAMPIONSHIP
PRELIMINARY PROPOSALS FOR
NEW RULES TO TAKE EFFECT ON 1 JANUARY 2008
Engine
  2.4 litre V8;
  maximum of four valves per cylinder;
  two-race engine (fool-proof method for ensuring this rule is observed, plus
carefully calculated penalty system for unscheduled changes);
  list of components which must be made from a specific material and/or using a
specified manufacturing process;
  ban on variable geometry inlet and exhaust systems;
  standard ECU (under FIA control)
  ban on ultra high pressure (direct injection) fuel systems enforced by means of
FIA ECU;
  maximum modulus of elasticity (stiffness) of materials reduced from 40 Gpa to 32
Gpa (throughout car).
Transmission, braking and steering
  manual gearbox with electronic over-rev safeguard;
  manually operated clutch;
  ban on electronically controlled differentials;
  ban on power steering systems;
  standard brake discs, pads and calipers.
Chassis
  weight limit reduced by at least 50 kilos (to eliminate ballast and thus reduce
kinetic energy in an accident);
  a combined tyre and aerodynamic package to be published no later than 31
December 2004 to achieve specific targets for cornering speeds, straight-line
speeds, grip and braking performance, taking weight reduction into acount;
  tyre (wheel) width reduced at front, increased at rear to allow weight distribution
consistent with no ballast and to give greater drag (total of front +rear widths to
stay same).
Sporting
  no spare car allowed during entire Event;
  cars to be held under parc fermé conditions during entire Event;
  one tyre supplier only, all sporting aspects of supply contract under control of FIA;
  drastic restriction on private testing, limited by mileage rather than number of
days, enforced by means of FIA ECU;
  two (identical) sets of tyres for qualifying and race;
  Friday practice: package to ensure cars run, possibly to include a qualifying
session;
  new qualifying system to be discussed with commercial rights holder
(broadcasters), teams and race promoters;
  if qualifying continues to be with race fuel, consider whether amount of fuel in
refuelling rig before race should be fixed annually in sporting regulations with
amount of fuel in car for qualifying and race free (to encourage fuel efficiency);
  no tyre change during race (except genuine puncture), refuelling to stay;
  consider if constructors’ points should be scored by a maximum of four specified
cars (two teams) per constructor (to encourage major teams to make cars and
information available to teams coming into Formula One, see below);
General
  no restriction on the sale, loan or exchange of chassis and components between
teams or to new entrants in the Championship;
  twelve entries to be accepted each year, entries to close on 1 July for following
season;
  guaranteed entries each year for teams with long-term contracts to compete in
Championship;
  technical and sporting rule changes for future seasons to be subject to a majority
vote of the teams already contracted to compete during the season in which the
rule changes will apply;
  technical rule changes concerning Formula One to be announced in June to take
effect on 1 January of the second year following the announcement (for example,
a technical rule change for 2012 would be announced no later than 1 July 2010,
having first been approved by a majority of the teams already contracted to
participate in 2012);
  no rule changes after entries close for a given Championship without consent of
all accepted teams.