Finnair hasn't decided anything yet but I would be surprised if Finnair would replace 11's with Boeing products, it really looks like Finnair is aiming for an all-airbus fleet.
So the next logical choice is propably A330/A340. Given the fact that A340-300 is actually smaller than the MD-11 and given another fact that Finnair has full-booked planes on HEL-JFK-HEL routes and charters flown by MD-11's. I wouldn't be surprised if Finnair would buy a couple of A340-500's or maybe even -600's.
There is also a small possibility that some of the MD-11's may be converted to freighters for Finnair Cargo, but who knows?