In a move that is annoying, yet not unexpected, UPN has formally canceled Star Trek Enterprise. The current Star Trek TV incarnation has suffered from low ratings, and lack of promotion by UPN, but has had a marked upturn in quality, so it makes it all the more annoying for fans who really liked the show.

You can read about the cancellation here and here.
Read this from the press release by UPN..
UPN and Paramount Network Television have jointly announced that this will be the final season of STAR TREK: ENTERPRISE on UPN
That text leads me to believe that the show might turn up back in syndication, which is how Star Trek: The Next Generation as well as Star Trek: Deep Space Nine were distributed. The press release specifically says “..the final season of Star Trek Enterprise on UPN”. They could have just said ‘final season of Star Trek Enterprise’ , and that would be it, but they added UPN. Perhaps it’s me hoping a bit too much, but I’d rather it go back to syndication. Especially now that the show has really discovered how to be Star Trek. It’s great again, and dammit. It gets cancelled.
If it really is gone gone, I hope we don’t get too long a break before Star Trek is back on TV. It’s been on TV with new episodes consistantly since 1987 – that’s a long time. Some might say that’s the reason it needs to go away for awhile, but I disagree. Enterprise was a great series, and especially Series 3 & 4. These two years of Star Trek were some of the greatest there’s been in years.