However, don't buy the Reuters alarmist spin. The actual statement by the President reads as follows:
As part of a final peace settlement, Israel must have secure and recognized borders, which should emerge from negotiations between the parties in accordance with UNSC Resolutions 242 and 338. In light of new realities on the ground, including already existing major Israeli populations centers, it is unrealistic to expect that the outcome of final status negotiations will be a full and complete return to the armistice lines of 1949, and all previous efforts to negotiate a two-state solution have reached the same conclusion. It is realistic to expect that any final status agreement will only be achieved on the basis of mutually agreed changes that reflect these realities.
There really isn't anything new here from the Taba agreements. This is highly neutral language - I mean, 1949? get a grip. The only date of any significance is 1967.
The "realities on the ground" broadly refer to the Israeli settlements (ie, the occupation), and as the unilateral withdrawal from Gaza indicates, are hardly permanent. I suspect that Bush's explicit reference here is more aimed at supporting Sharon's intention to keep Hebron.
Note that you could easily draw an opposite interpretation of bias from the President's statement:
As the Government of Israel has stated, the barrier being erected by Israel should be a security rather than political barrier, should be temporary rather than permanent, and therefore not prejudice any final status issues including final borders, and its route should take into account, consistent with security needs, its impact on Palestinians not engaged in terrorist activities.
The point here is that there is no sea change in policy, but rather a targeted re-emphasis of the same old policy, with some flexibility to give Sharon the political breathing room he needs to unilaterally withdraw from Gaza (a move that Egyptrian President Hosni Mubarak also approves of strongly).
For more context on the Gaza withdrawal, Sharon's intention to retain Hebron, and the statement by the President after meeting with Sharon, see Jonathan Edelstein's much more in-depth analysis.
UPDATE: Jonathan has extended comments on the issue - essential reading.