They will steadily rise IMO.
I want to move in 5 years or so, depending on the secondary school I want my daughters to attend. My aim for the moment is to pump as much as possible into my current mortgage, so that in 5 years I can remortgage this property and use that money as a deposit for another, without having to sell this place. That way, I get my new property to move into, while keeping this one (maybe with a large mortgage though) to put on rent. As long as the rent covers the mortgage payments Im not too bothered with how big the mortgage is on this property once Ive moved.
Hence, Im hoping they dont increase too much, but Im pretty certain they will climb, although very gradually.