There have been 'strong' rumours about American Airlines but it seems that the BHX initiative has scotched any chance there might have been there. United has also been mentioned but it may have all started with the comment of the BRS CEO earlier this year when he spoke of something happening in 'the very near future'.
As for Ryanair they've been fairly static at BRS for several years although some routes have come and gone to be replaced by others.
It looks as though the future is increasingly orange with strong hints from quarters that should not be lightly dismissed that there is more to come as there is with bmi regional.
One negative piece of news is that Helvetic appears to have pulled out altogether according to an email sent to a poster on another forum.