EIR offers USA connections so I can't see why they wouldn't stay. EIR competes against Ryanair (3 x daily) at BRS yet have remained there for a number of years in that situation. I would have thought that Ryanair would present a bigger competitor than Flybe so again I can see no reason for EIR to leave CWL.
Incidentally, the CAA stats for May were published today. CWL's monthly passenger total was slightly down on last year at under 106,000 and the rolling 12-month total slipped just below the one million mark.
However, the rest of the year should see some substantial passenger number rises as the Fiybe base begins to make its presence felt.