Blues and Ospreys forced to find new homes?

http://www.kumb.com/story.php?id=125879

Interesting little article here about West Hams refusal to move into the the Olympic Stadium with a rugby team, because:

"While all of us at West Ham would be happy to share with athletics at the Olympic stadium, there is no way we would go into a ground-sharing agreement with a rugby club. It is a complete non-starter for us.

"Impossible, actually, as soon it will be a breach of Premier League rules to share your ground with rugby."

Now if the Premier League does in fact force this rule, and knowing that both Swansea and Cardiff football clubs have the first choice lease on the stadium use, where does this leave the Blues and Ospreys?
Wigan Warriors Rugby League team could also be effected.

There have been many rumours of the Blues moving back to the Arms Park, and the Ospreys moving to Bridgend, well maybe this is why.

This could affect a great deal of top teams throughout England and Wales.

I think that rule only applies if the agreement to stadium share was made whilst the Football team is in the premiership,
not like Swansea F.C who were in the league below when they went in to agreement with the Mighty Ospreys, same for Cardiff City