The Jet2 S10 schedule was on sale before the Ryanair news broke. Compared to this summer it appears they have reduced flights on many routes.
Bridgepoint have always stated their intention to grow the airport to 5m passengers and some of that growth needs to come from other carriers. I think Jet2 may have been a little foolish if they thought they would be allowed to maintain their monopoly long term.
More new destinations would of course be good but there is demand for the key bucket & spade routes that remains unsatisfied at Leeds.
As for a bloodbath: There is no benefit to the airport in replacing one near monopoly provider with another and whilst market forces will play a part I strongly believe there is capacity for both carriers on these key routes.
Interesting times ahead!