Speaking as someone who rents myself, I'll pay the market rate and no more even if the landlord tells me "This year is an exception, I will be raising the rent next year because of my costs". Next year is a whole new ballgame - I'm not in the business of making friends with my landlord, I simply expect a professional service from him while I uphold my side of the agreement. I don't know many landlords out there who didn't increase rents when it was a strong rental market, now that the market has turned (at least from my viewpoint) landlords will have to start accepting lower rents. Simple supply and demand.
On the question itself, from personal experience of filling rooms in a house (can't quote any statistics), it has become an awful lot harder to fill rentals. A couple of years ago, the phone would never stop ringing when you put an ad in daft or the herald, this year (and last year) you would get 2 or 3 people around in a week, and you'd have to accept people you previously wouldn't have considered. If I was a landlord, I would want to hang on to "good" tenants (once they agree a reasonable rent), particularly with a view to the medium term direction of the market.