The handicapped seats are reserved for gate assignment to those with disabilities. You will be fine unless someone checks in that is elderly, has trouble walking or has requested wheel chair assistance. If there is someone that is handicapped or disabled than the gate agent has every right to and most likely will move you to any availble Y seat to put the handicapped or disabled person and if they have a companion in those seats. If I were you I would hack into another seat. You might get to keep it, but how many flights have zero people in wheelchairs? Very, very few. That is why those seats are reserved and if assigned ahead of time are always subject to re-assingment.