Ultimately, yeah, but the underlying question behind the question is why did so many viewers just stop tuning into DS9? DS9 ran so long without any peril because it was the #2/#1/#2/#3/#1 show in syndication over its run and the actors (minus Farrell) could be signed back easily. Voyager was the #1, then #2 rated show on UPN (always #1 in scripted television, though I laugh at saying that because wrestling is so obviously scripted). And if it were in synd., Voyager would've had good enough numbers to air all 7 seasons, though there was a brief issue with contract extension negotiations with Mulgrew after Season 5 (same with Stewart after Season 3). Voyager had a contrast with DS9. It looks like Ryan wanted to be on Boston Public/the show wanted her, but she finished Voyager's 7th season instead of hopping over to Boston Public, unlike Farrell, who was supposedly asking for as much pay as Brooks was getting for Season 7.Not sure why it matters that the ratings dropped - the ratings stayed high enough to be renewed for a full seven seasons.
Sorbo wanting to leave/refusing negotiations is what ended Hercules, not ratings. Xena, it was a combo of increasing production costs/declining ratings, some staff burnout and the syndication market beginning to implode. The 2000-01 season was the worst year for ad revenue for tv stations in 50 years. Not sure if any year since then topped it. After that season, for other reasons importantly too, the whole first-run syndication market just disintegrated.