In the original rumor, the phone was rumored to be launching around the end of July/beginning of August, and as of now, July is out of the question obviously. Middle August to early September is probably a more likely timeframe.
Unfortunately, even with that extra time, it is not likely that the high-end handset will launch with Android 2.1. The last time I heard news about the software update for the Xperia X10, the "latter part of Q3 and onwards" were the words Sony Ericsson used to indicate the launch timeframe.
Engadget reports that they believe the launch to be in a few weeks:
We're hearing that AT&T is lining up for a launch some time between the middle of August and the middle of September; smartphone data is required, of course, and it'll cost independent dealers $345 per unit (retail pricing is anyone's guess).
BoyGeniusReport writes that they were informed of an upcoming release by a tipster:
We have been told that the Sony Ericsson X10 has finally passed through AT&T’s technical acceptance process and should be available in the “coming weeks.” We don’t have any sort of pricing, but we’d wager a $149-$199 price point with a two year agreement. Lastly, the other SE handset, the Vivaz (codenamed Monet) should be hitting the Death Star carrier as early as September.
Phandroid adds that the phone may launch with Wi-Fi problems, and that AT&T will likely tamper with the handset's insides before they push it out to consumers.
Image from Engadget