I've found an article that seems to put down all the rumors on a Balto 4...
It can be found here : The article state that "According to the recent news on the expansion of the Universal Home Entertainment Productions division (UHEP), big changes were expected. [...] Due to the poor sales performed by the latest installment in the Balto series, Universal Home Entertainment Productions does not plan any new sequel to the Balto franchise. However, a decision has been taken to bring back another old Amblin animated feature, An American Tail. A new series is currently in production, starting with the brand new title "An American Tail : The great migration", exclusively for the dvd market."

It also speaks about new licenses aimed at young children, and shows sales figures for the year 2004. Everyone is of course invited to comment on this news, which to me is rather unexpected considering the fact that I thought Balto 3 made good sales...

EDIT : To everyone who didn't understand yet, this was only an april fool joke...And a little to test you, too ^^ It shows most of you would want a Balto 4, then.
This scenario could be possible, but I believe Universal is not decided to stop with the sequels yet.
Now, everyone keep his opinion on if it's a good thing or not...But I think most of you must be rather relieved.