if you listen to the live stream, it definitely doesn't say conclusively that it will work.
They stated that the update for Gear compatibility will come in October for the S4 and that the S3 and Note 2 will be getting updates in October as well, but didn't say it was for the Gear. Not sure our phones have the newest BT low energy that the watch pairs to. The S4 does.
Even the tech sites are divided. The verge says it will work, engadget says S4 only:
Perhaps the biggest setback, however, is that the Galaxy Gear is only compatible with the Note 3 and the new Note 10.1, and while it will likely work with the GS4 once that device gets an Android 4.3 update, we don't expect that it'll ever function with non-Samsung smartphones and tablets.